Test create snippet abilities for external users for both personal
snippets and project snippets.

Snippet repositories will be phased in. Currently endpoint URLs are
dependent on the snippet itself being attached to a repository, and the
version_snippet feature flag setting.

When the snippet content we need to replicate it
to the snippet repository.

In the same operation where the snippet and
its repository is created, commit the file
into it.

243 files inspected, 343 offenses detected, 343 offenses corrected

Changes `set` to `let_it_be`

Part of a general tidy of spam logic

Ran: bundle exec rubocop --only RSpec/EmptyLineAfterFinalLet -a

Auto-correct some references in RSpec as:
- expect_any_instance_of -> expect_next_instance_of
- allow_any_instance_of -> allow_next_instance_of

Related to https://gitlab.com/gitlab-org/gitlab/issues/34997

Partially addresses:

https://gitlab.com/gitlab-org/gitlab/issues/27703

- only for issues and merge requests
- snippets still require solving reCaptcha

rails_helper.rb's only logic was to require
spec_helper.rb.

rails_helper.rb's only logic was to require
spec_helper.rb.

When a restricted visibility level of `private` is set in the instance,
creating a snippet with the `visibility` level would always fail.
This happened because:

1. `params[:visibility]` was a string (e.g. "public")
2. `CreateSnippetService` and `UpdateSnippetService` only looked
   at `params[:visibility_level]`, which was `nil`.

To fix this, we:

1. Make `CreateSnippetService` look at the newly-built
   `snippet.visibility_level`, since the right value is assigned by the
   `VisibilityLevel#visibility=` method.
2. Modify `UpdateSnippetService` to handle both `visibility_level` and
`visibility` parameters.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/66050

Previously, you could only access personal snippets in the API if you
had authored them. The documentation doesn't state that this is the
case, and it's quite surprising.

Updates specs to use new rails5 format.

The old format:
`get :show, { some: params }, { some: headers }`

The new format:
`get :show, params: { some: params }, headers: { some: headers }`

Updates specs to use new rails5 format.

The old format:
`get :show, { some: params }, { some: headers }`

The new format:
`get :show, params: { some: params }, headers: { some: headers }`

Merge branch 'security-10-4-25223-snippets-finder-doesnt-obey-feature-visibility' into 'security-10-4'

[Port for security-10-4]: Makes SnippetFinder ensure feature visibility

Merge branch 'security-10-4-25223-snippets-finder-doesnt-obey-feature-visibility' into 'security-10-4'

[Port for security-10-4]: Makes SnippetFinder ensure feature visibility

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Removed all the unnecessary include of `WaitForAjax` and `ApiHelpers` in the specs.
Removed unnecessary usage of `api:true`