Revert MattermostNotificationService and SlackNotificationService to MattermostService and SlackService

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

We cant have project with name 'project' or 'tree' anymore.
This merge request containts a migration that will find and rename all
projects using reserved names by adding N digit to the end of the name.
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This adds counters for build artifacts and LFS objects, and moves
the preexisting repository_size and commit_count from the projects
table into a new project_statistics table.

The counters are displayed in the administration area for projects
and groups, and also available through the API for admins (on */all)
and normal users (on */owned)

The statistics are updated through ProjectCacheWorker, which can now
do more granular updates with the new :statistics argument.

This adds a migration to remove unused services, where the properties
are empty. As the properties are empty, those do not contain any
settings or other information.

Fixes #25727

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

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

Currently namespace name and path have uniq validaiton which does not
allow us to use same group name/path inside different groups. This
commit changes validation in next way:

* Allow same namespace name with different parent_id
* Allow same namespace path. Uniq validation should be handled by routes table
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

* add parent_id field to namespaces table to store relation with nested groups
* create routes table to keep information about full path of every group and project
* project/group lookup by full path from routes table
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This new global setting will allow admins to specify if HTML emails should be sent or not,
this is basically useful when system administrators want to save some disk space by avoiding
emails in HTML format and using only the Plain Text version.

Closes #23150

This prevents leakage of project names on an endpoint which is
unauthenticated and thus open to the world.

The database should not have any soft-deleted groups. Due to a race
condition (soft-delete completes after the hard-delete), soft-deleted
groups were (incorrectly) left in the database, causing issues while
trying to create a new group with the same name.

add pipeline id to merge request metrics table. Also, updated the pipeline worker to populate this field.

Improves documentation

Adds tests

Fix prop validation for objects

Finish tests for environment item

Adds tests for toggle folder function

Environment tests

Adds tests

See https://gitlab.com/gitlab-org/gitlab-ce/issues/24386

   Set request access for projects/groups to false by default.
   Request access implemented in !5286 8.10 was enabled by default.

The AddVisibilityLevelToGroups migration introduced a visibility_level for
namespaces and specified that projects should always have a visibility level
less than or equal to their namespace. However, some invalid rows could have
been created.

This commit introduces a migration that updates the invalid rows, setting the
invalid project to have the same visibility_level as their namespaces. This
will make some projects internal or private when they would previously have
been public or internal, but this is better than silently making an internal
or private group public.