- Add new service that transfers milestones
from a group to a project
- Include new service in Projects transfer service
- Include FromUnion module in Milestone model
to use in transfer service
- Add specs for new milestones service
- Add specs for transferring milestones in
project transfer service

- Externalize strings in milestones_helper
- Externalize strings in app/services
- Update PO file

Instead of querying relations into ids we just pass them to the model
scope because the scope supports it now.

Also changes other calls to `Milestone.for_projects_and_groups`

This whitelists all existing offenses for the various CodeReuse cops, of
which most are triggered by the CodeReuse/ActiveRecord cop.

This whitelists all existing places where we use "destroy_all".

Partially addresses #47424.

some changes introduced by 4daa6da5, 26b6e299, 17898ce0 were regressed during today's merge conflict resolution of !11573.

This commit serves to reapply those changes.

/cc: @rspeicher @stanhu @mikegreiling

* Remove call to Milestone#save! instead just Milestone#save
* Add safety specs to stop a regression

Fixes #22033

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

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

Reported by https://github.com/gitlabhq/gitlabhq/issues/9643

for posterity.

Also fix issue where destroying a Milestone would cause odd, transient messages like
"created milestone" or "imported milestone".

Add "in" preposition when creating and destroying milestones

Closes #2382

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

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

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