Explored Policy framework to create something I can use as a starting point.

The query becomes a lot simpler if we can check the branch name as
well instead of having to load all branch names.

When an MR is created using `allow_maintainer_to_push`, we enable some
abilities while the MR is open.

This should allow every user with developer abilities on the target
project, to push to the source project.

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>

This commit also makes spec/policies/namespace_policy_spec.rb file
to be compatible with the same file in GitLab EE.

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

…in Groups::UpdateService instead of only in the browser.

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

Remove superfluous lib: true, type: redis, service: true, models: true, services: true, no_db: true, api: true

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

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

The `members` table can have entries where `user_id: nil`, because people can
invite group members by email. We never want to include those as members,
because it might cause confusion with the anonymous (logged out) user.