The api will proxy requests to the environment's prometheus server.
The Prometheus::ProxyService class can be reused when we add support for
group prometheus servers.

- Use strong_memoize for prometheus_adapter since it can be nil in some
cases.
- Do not phrase spec descriptions with 'should'.

- This is so that we don't have to check that params is of type
ActionController::Parameters in ProxyService.

- Permit params in ProxyService class to avoid having to make changes
to both ProxyService and to PrometheusApiController when adding support
for more prometheus apis.
- Also refactor the cache specs.

- proxyable is a better name for any model object that has a prometheus
server to which requests can be proxied.

- It is unlikely that we will stop supporting prometheus APIs that were
previously supported.

- Add a method for returning a service_unavailable response.
- Keep only one spec to test that the prometheus response is returned
as-is.

- calculate_reactive_cache does not need to initialize @prometheus_owner
again. It's already being initialized in the initialize method.

- The service uses the PrometheusClient.proxy method to call the
Prometheus API with the given parameters, and returns the body and
http status code of the API response to the caller of the service.
- The service uses reactive caching in order to prevent Puma/Unicorn
threads from being blocked until the Prometheus API responds.

- Also refactor the get and json_api_get methods so that the get method
can be reused by the new proxy method.
- The new proxy method makes no changes to the request to the prometheus
server and response from the prometheus server. This allows it to be
used as a proxy to the Prometheus server, hence the name.

Drop legacy artifacts usage as there are no leftovers

See merge request gitlab-org/gitlab-ce!24294

Fix a KeyError in GitlabSchema

Closes #60057

See merge request gitlab-org/gitlab-ce!27011

Rename Workhorse terminal_specification to channel_specification

See merge request gitlab-org/gitlab-ce!26939

We're moving from using terminology related to terminals when
we refer to Websockets connections in Workhorse.
It's more appropiate a concept like channel.

Allow reactive caching to be used in services

See merge request gitlab-org/gitlab-ce!26839

Add support for defining a reactive_cache_worker_finder function
that will be used by the reactive_caching_worker to generate/initialize
the calling object. This allows reactive caching to work with Services
where the object cannot be obtained from DB but a new object can be
initialized.

Allow GraphQL Scalar-fields to be authorized

Closes #57831

See merge request gitlab-org/gitlab-ce!26338

Externalize strings in helpers

See merge request gitlab-org/gitlab-ce!26845

- Update qa selector
- Update PO file

Fix vue render error for IDE status bar

Closes #59995

See merge request gitlab-org/gitlab-ce!26979

Allow to sort wiki pages by date and title

See merge request gitlab-org/gitlab-ce!25365

- Add controls for sorting by title and date
- Execute Gitaly call which now accepts sorting params for wikis

Update GitLab Shell to v9.0.0

See merge request gitlab-org/gitlab-ce!27002

Basic limiting complexity of GraphQL queries

Closes #58405

See merge request gitlab-org/gitlab-ce!26629

Resolve "Automatically set Prometheus step interval"

Closes #58839

See merge request gitlab-org/gitlab-ce!26441

By computing the step interval passed to the query_range Prometheus API
call we improve the performance on the Prometheus server and GitLab by
reducing the amount of data points sent back and prevent Prometheus
from sending errors when requesting longer intervals.

Resolve "Failing group transfer disables expandable sections"

Closes #45511

See merge request gitlab-org/gitlab-ce!26837

Extract confidential quick action spec to a shared example

Closes #59570

See merge request gitlab-org/gitlab-ce!26913

Add a link to S3 Permission Scopes for registry object storage

Closes #58881

See merge request gitlab-org/gitlab-ce!26067

Allow to use untrusted ruby syntax

See merge request gitlab-org/gitlab-ce!26905