* Allow domain blocks to reject media without silencing or suspending

* Fix typo

* Hide 'Reject media' button when superfluous, instead of disabling it

* Properly hide 'reject media' checkbox on page load if needed

This may happen when resubmitting the domain block form after an error.

* Don't ask whether undoing a media-only block should be retroactive

* Rename :media_only block to :noop

* Display :noop block as None in frontend, allow blocks that do nothing

* Remove 'coding' line auto-added by emacs

* Add spec for unblock domain service

* Refactor UnblockDomainService

* Set domain_block by before_action

* Cast value with ActiveRecord::Type

* Batch update

Create MediaAttachment but without actual file download when domain is blocked with reject_media set to true
Clean up old media files when creating a new domain block with reject_media set to true
Return remote_url in media attachments API if local file is not present
Undo domain block action in admin UI
Ability to enable reject_media from admin UI