We are removing one-click applications from GitLab but leaving the
integrations for Prometheus and Elastic Stack.

We have code in place that keeps the integration in sync with the
corresponding cluster application, and have backfilled the
ingtegrations, so we can now use them as a source of truth.

See

- Backfill Prometheus: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61502
- Backfill Elastic Stack: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/61521
- Deprecation Epic: https://gitlab.com/groups/gitlab-org/-/epics/4280

When we added Helm 3 support, I missed testing Knative
installation. We have now fixed the chart upstream, see
https://gitlab.com/gitlab-org/charts/knative/-/merge_requests/9
There are no other significant changes.

With this change, any existing cluster will continue to use
Helm 2, while all new clusters will use Helm 3 for GitLab-managed apps.
Note that this only applies to GitLab-managed apps -- Auto DevOps
uses its own Helm version on a per-project basis.

The diff looks big because we split the Helm command classes into two
modules, V2 and V3, to allow them to evolve independently as long as
they both implement the same minimal interface.

The command classes in the V2 module should be exactly equal to their
old counterparts, besides the addition of BaseCommand#helm_version,
which the common Kubernetes pod generator uses to resolve the container
image.

The command classes in the V3 module are ports of the relevant subset of
commands. There are more classes in the V2 module because we carried
along support for in-cluster Tiller. This is currently unused, but may
be used to clean up Tiller if we decide to offer Helm 2 to 3 migration
in the product later on.

See also https://gitlab.com/gitlab-org/gitlab/-/issues/120021

So that we can scope the feature flag to the entity that owns the
cluster (project, group or instance).

Move scheduling of the worker out of BaseService and make it
part of a state transition (after make_install happens). This
ensures that Knative is installed before we attempt to update it.

- Serialize available domains and currently associated domain when
  presenting Knative
- When Knative is updated, create an association to the newly
  selected domain

Relates to https://gitlab.com/gitlab-org/gitlab/issues/33559

- Encapsulate functionality for parsing and
  generating function URIs in
  Gitlab::Serverless::FunctionURI
- Update references to Serverless with global
  scope operator
- Delegate Serverless::DomainCluster#domain to
  PagesDomain

Relates to https://gitlab.com/gitlab-org/gitlab/issues/195964

Instead we can call the original method if the cluster is RBAC. The
original method already checks if helm is available, and that it is not
not_installable

- Tracks likst of api_groups instead of CRDs (much smaller)
- Adds kubectl command to fetch api resources by api group
- Adds kubectl command to delete api resources by api group
- Adds/Updates specs

- Permits cloud_run parameter in ClustersController#create
- Enables httpLoadBalancing, istioConfig, and cloudRunConfig in
  Gcp ProvisionService if cloud_run is enabled
- Add `Enable Cloud Run on GKE` checkbox to cluster create page
- Add `Enable Cloud Run on GKE` checkbox to cluster details
- Default knative to pre_installed for cloud_run clusters
- Make knative not uninstallable for pre_installd clusters
- Update project clusters docs with entry about Cloud Run
- Update tests and add new test for cluster with cloud_run enabled
- Add Cloud Run on GKE strings to translations
- Add spec that will fail when google-api-client has been upgraded
- Add pre_installed to applications frontend
- Pass providerType and preInstalledKnative to frontend
- Display `installed via` on frontend for Cloud Run
- Add Cloud Run spec for FinalizeCreationService

Relates to https://gitlab.com/gitlab-org/gitlab/issues/27502

- refactor Knative and Prometheus

- After uninstalling the knative helm chart it's necessary to also
remove some leftover resources to allow the cluster to be clean
and knative to be reinstalleable.
- Adds knative uninstall disclaimer
- Uninstall ksvc before uninstalling knative

Make list of Knative and Ingres resources explicit

- To avoid deleting unwanted resources we are listing exact
which resources will be deleted rather than simply deleting any
resource that contains istio or knative words.

Remove Kn services cache from Clusters::Application::Knative

Knative function can exist even if user did not installed Knative via
GitLab managed apps.

-> Move responsibility of finding services into the Cluster
-> Responsability is inside Clusters::Cluster::KnativeServiceFinder
-> Projects::Serverless::FunctionsFinder now calls depends solely on a
cluster to find the Kn services.
-> Detect Knative by resource presence instead of service presence
-> Mock knative_installed response temporarily for frontend to develop

Display loader while `installed === 'checking'`

Added frontend work to determine if Knative is installed

Memoize with_reactive_cache(*args, &block) to avoid race conditions

When calling with_reactive_cache more than once, it's possible that the
second call will already have the value populated. Therefore, in cases
where we need the sequential calls to have consistent results, we'd fall
under a race condition.

Check knative installation via Knative resource presence

Only load pods if Knative is discovered

Always return a response in FunctionsController#index

- Always indicate if Knative is installed, not installed or checking
- Always indicate the partial response for functions. Final response is
guaranteed when knative_installed is either true | false.

Adds specs for Clusters::Cluster#knative_services_finder

Fix method name when calling on specs

Add an explicit check for functions

Added an explicit check to see if there are any functions available

Fix Serverless feature spec

- we don't find knative installation via database anymore,
rather via Knative resource

Display error message for request timeouts

Display an error message if the request times out

Adds feature specs for when functions exist

Remove a test purposed hardcoded flag

Add ability to partially load functions

Added the ability to partially load functions on the frontend

Add frontend unit tests

Added tests for the new frontend additions

Generate new translations

Generated new frontend translations

Address review comments

Cleaned up the frontend unit test.
Added computed prop for `isInstalled`.

Move string to constant

Simplify nil to array conversion

Put knative_installed states in a frozen hash for better read

Pluralize list of Knative states

Quey services and pods filtering name

This way we don't need to filter the namespace in memory.
Also, the data we get from the network is much smaller.

Simplify cache_key and fix bug

- Simplifies the cache_key by removing namespace duplicate
- Fixes a bug with reactive_cache memoization

Remove Kn services cache from Clusters::Application::Knative

Knative function can exist even if user did not installed Knative via
GitLab managed apps.

-> Move responsibility of finding services into the Cluster
-> Responsability is inside Clusters::Cluster::KnativeServiceFinder
-> Projects::Serverless::FunctionsFinder now calls depends solely on a
cluster to find the Kn services.
-> Detect Knative by resource presence instead of service presence
-> Mock knative_installed response temporarily for frontend to develop

Display loader while `installed === 'checking'`

Added frontend work to determine if Knative is installed

Memoize with_reactive_cache(*args, &block) to avoid race conditions

When calling with_reactive_cache more than once, it's possible that the
second call will already have the value populated. Therefore, in cases
where we need the sequential calls to have consistent results, we'd fall
under a race condition.

Check knative installation via Knative resource presence

Only load pods if Knative is discovered

Always return a response in FunctionsController#index

- Always indicate if Knative is installed, not installed or checking
- Always indicate the partial response for functions. Final response is
guaranteed when knative_installed is either true | false.

Adds specs for Clusters::Cluster#knative_services_finder

Fix method name when calling on specs

Add an explicit check for functions

Added an explicit check to see if there are any functions available

Fix Serverless feature spec

- we don't find knative installation via database anymore,
rather via Knative resource

Display error message for request timeouts

Display an error message if the request times out

Adds feature specs for when functions exist

Remove a test purposed hardcoded flag

Add ability to partially load functions

Added the ability to partially load functions on the frontend

Add frontend unit tests

Added tests for the new frontend additions

Generate new translations

Generated new frontend translations

Address review comments

Cleaned up the frontend unit test.
Added computed prop for `isInstalled`.

Move string to constant

Simplify nil to array conversion

Put knative_installed states in a frozen hash for better read

Pluralize list of Knative states

Quey services and pods filtering name

This way we don't need to filter the namespace in memory.
Also, the data we get from the network is much smaller.

Simplify cache_key and fix bug

- Simplifies the cache_key by removing namespace duplicate
- Fixes a bug with reactive_cache memoization

Only prometheus can be uninstalled atm, the rest will be dealt with
later.

Presumption is that new application types will have uninstallation
implmemented at the same time.

This is a gitlab-ee port of the following gitlab-ce MR:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/25181

Before_transition does not play nice when used with
OptimisticLocking and this can result in triggering
multiple events

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55306

Before_transition does not play nice when used with
OptimisticLocking and this can result in triggering
multiple events

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55306