Due to a bug, some pool_repositories in production have a null
source_project_id column. This migration aims to fix those rows.

Add project level git depth setting

Closes #59688

See merge request gitlab-org/gitlab-ce!28919

Save certificate validity time for pages domains on save
Fill validity time for existing pages domains in background migration

This reverts merge request !28743

Save certificate validity time for pages domains on save
Fill validity time for existing pages domains in background migration

We need to stub default_git_depth and default_git_depth= because some
old migrations specs try to create a record using schema before that
column was introduced.

Introduce default_git_depth in project's CI/CD settings and set it to
50. Use it if there is no GIT_DEPTH variable specified. Apply this
default only to newly created projects and keep it nil for old ones
in order to not break pipelines that rely on non-shallow clones.

default_git_depth can be updated from CI/CD Settings in the UI, must be
either nil or integer between 0 and 1000 (incl).

Inherit default_git_depth from the origin project when forking projects.

MR pipelines are run on a MR ref (refs/merge-requests/:iid/merge) and it
contains unique commit (i.e. merge commit) which doesn't exist in the
other branch/tags refs. We need to add it cause otherwise it may break
pipelines for old projects that have already enabled Pipelines for merge
results and have git depth 0.

Document new default_git_depth project CI/CD setting

When a Group is missing a route, the migration failed previously with a
`Invalid single-table inheritance type` error. To fix this, we can
disable STI for the migration class because we don't need to know about
the type to do this migration. Besides, currently Group is the only type
used in the type column.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/58714

Reset merge status from mergeable MRs

See merge request gitlab-org/gitlab-ce!28843