Keeps existing behaviour for ABAC cluster

Explicitly persist the legacy_abac value of the cluster_provider_gcp so that we can disable abac if the `:rbac_clusters` feature flag is enabled

Fix spec warning: removing `initialize' may cause serious problems

Actually verify that `service.create_cluster` is called with expected
request_body and other args

Only create new service account with cluster-admin clusterrolebinding for when we have the rbac cluster FF enabled.

This syncs up with `authorization_type`.

Adds "More information" link from the RBAC cluster form element to the documentation from the previous commit

This is the same as with adding an existing cluster

When provisioning a new cluster, create gitlab service account so that GitLab can perform operations in a RBAC-enabled cluster.

Correspondingly, use the token of the gitlab service account, vs the
default service account token which will have no privs.

This is in preparation to share some common code with another service
which will also need a kubeclient utilizing master username and password

Enable frozen string in app/graphql + app/finders

See merge request gitlab-org/gitlab-ce!21681

Update Gitlay server version to 0.121.0

See merge request gitlab-org/gitlab-ce!21725

Fixed resolved discussions not toggling expanded on changes tab

Closes #51370

See merge request gitlab-org/gitlab-ce!21676

Fix column differences in `db/schema.rb`

See merge request gitlab-org/gitlab-ce!21718

Add project to jupyter cluster app factory spec

See merge request gitlab-org/gitlab-ce!21717

Document abstraction levels and code reuse

See merge request gitlab-org/gitlab-ce!21254

This is based on the discussion in
https://gitlab.com/gitlab-org/gitlab-ce/issues/49653 and the example
merge request found at
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20908. The idea
is fairly straightforward: we define a variety of abstractions, then
state which can reuse which. This should ultimately foster _better_ code
reuse, make it easier to debug problems, and make it harder to
accidentally introduce a performance regression.

Add RuboCop cops to enforce code reusing rules

See merge request gitlab-org/gitlab-ce!21391

Enable omniauth by default

Closes #49990

See merge request gitlab-org/gitlab-ce!21700

Display click to expand on collapsed diffs

Closes #51466

See merge request gitlab-org/gitlab-ce!21716

project_custom_attributes and group_custom_attributes used datetime
instead of datetime_with_timezone column type in database schema. But
actually migration defines `t.timestamps_with_timezone`.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Merge branch '50808-choosing-initialize-repo-with-a-readme-breaks-project-created-from-template' into 'master'

Resolve "Choosing “Initialize repo with a README” breaks project created from template"

Closes #50808

See merge request gitlab-org/gitlab-ce!21646

Vendor Auto-DevOps.gitlab-ci.yml: fix where the deploy job does not wait for Deployment to complete.

Closes #50186 and charts/auto-deploy-app#6

See merge request gitlab-org/gitlab-ce!21713

Vendor Auto-DevOps.gitlab-ci.yml for refactor to create registry_login() function.

Closes #51450

See merge request gitlab-org/gitlab-ce!21714

Fix route deprecation warnings in rails 5

See merge request gitlab-org/gitlab-ce!21684

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51370

Merge branch '42861-move-include-external-files-in-gitlab-ci-yml-from-starter-to-libre' into 'master'

Resolve "Move "include external files in .gitlab-ci.yml" from Starter to Libre"

Closes #42861

See merge request gitlab-org/gitlab-ce!21603

Vendors in Auto-DevOps.gitlab-ci.yml from
https://gitlab.com/gitlab-org/gitlab-ci-yml/merge_requests/195

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/50186

Vendor Auto-DevOps.gitlab-ci.yml from https://gitlab.com/gitlab-org/gitlab-ci-yml/merge_requests/193

Thanks @LaurentGoderre, for your contribution !

Strip whitespace from Sentry URL

Closes #49621

See merge request gitlab-org/gitlab-ce!21703

[ci skip]

Resolve "500 Internal Server Error: Deleting branch of deleted project"

Closes #50678

See merge request gitlab-org/gitlab-ce!21542