see https://gitlab.com/gitlab-org/gitlab-ce/issues/42025

- Better gitaly-handling in /api/internal/allowed specs

And use .rubocop.yml to exclude paths we don't care,
rather than using the cop itself to exclude.

Adds a rubocop rule (with autocorrect) to ensure line break after guard clauses.

The initializers including this were doing so at the top level, so every object
loaded after them had a `current_application_settings` method. However, if
someone had rack-attack enabled (which was loaded before these initializers), it
would try to load the API, and fail, because `Gitlab::CurrentSettings` didn't
have that method.

To fix this:

1. Don't include `Gitlab::CurrentSettings` at the top level. We do not need
   `Object.new.current_application_settings` to work.
2. Make `Gitlab::CurrentSettings` explicitly `extend self`, as we already use it
   like that in several places.
3. Change the initializers to use that new form.

And the link to the last page cannot be `page=0`.

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

- Make single gitaly payload
- Add feature-flag specs to verify payload

This new param allows us to share project information between components
that don't share or don't have access to the same filesystem
mountpoints, for example between Gitaly and Rails or between Rails and
Gitlab-Shell hooks. The previous parameters are still supported, but if
found, gl_repository is prefered. The old parameters should be deprecated
once all components support the new format.

Refactored specs and added a post deployment migration to remove the activity users table.

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