Follow-up to d05dd81b which changed the nested namespaces in projects
to use API::Entities::Namespace instead of exposing all fields.

Fixes #27730

The create and edit actions for projects had these parameters:

- `public` (optional) - if true same as setting `visibility_level = 20`
- `visibility_level` (optional)

Remove the `public` parameter to avoid contradiction.

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.

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

You can only assign default_branch when editing a project or when creating a project for a specified user [ci skip]

You can only assign default_branch when editing a project [ci skip]

[ci skip]

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

The UI allows to define a token to validate payload on the target URL,
this patch adds the feature to the API.

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

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

FIxes #19361, #3119.

Browser interface allows forking to an owned grup.
This commit brings API up to speed by providing optional namespace
parameter to fork API. This allows forking to users and groups under
forker's control using their id or unique name.

Fixes #21591

[ci skip]

[ci skip]

The wrong example for "Branches".
Added option parameters in protect branch section.
Here is reason: https://gitlab.com/gitlab-org/gitlab-ee/commit/3ab07b8aae8dae43cfa3aae1306c59ea264a8594

Maybe this section could/should be deleted. Because in file repositories.md it had been deleted:  https://gitlab.com/gitlab-org/gitlab-ee/commit/8f3701eff005aeedcebff8ce02074f5056a369b3

Also, mutualize AccessRequests and Members endpoints for Group &
Project.
New API documentation for the AccessRequests endpoints.
Signed-off-by: NRémy Coutable <remy@rymai.me>

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