* Add moderation warnings

Replace individual routes for disabling, silencing, and suspending
a user, as well as the report update route, with a unified account
action controller that allows you to select an action (none,
disable, silence, suspend) as well as whether it should generate an
e-mail notification with optional custom text. That notification,
with the optional custom text, is saved as a warning.

Additionally, there are warning presets you can configure to save
time when performing the above.

* Use Account#local_username_and_domain

* Add confirmation page for suspensions

* Suspension confirmation closes reports, linked from report UI

* Fix tests

* Implement Assignment of Reports (#6967)

* Change translation of admin.report.comment.label to "Report Comment" for clarity

As we'll soon add the ability for reports to have comments on them, this clarification makes sense.

* Implement notes for Reports

This enables moderators to leave comments about a report whilst they work on it

* Fix display of report moderation notes

* Allow reports to be reopened / marked as unresolved

* Redirect to reports listing upon resolution of report

* Implement "resolve with note" functionality

* Add inverse relationship for report notes

* Remove additional database querying when loading report notes

* Fix tests for reports

* Fix localisations for report notes / reports

* Simplify admin/reports controller filtering for index

* Rename parameter to resolved

* Fix issue where reports view could not access filter_link_to

* Add coverage for admin/reports controller

* DRY up resolution of related reports for target account

* Clean up admin/reports routes

* Add Report#statuses method

* DRY up current account action taken params

* Rubocop styles

* Add Admin::BaseController to wrap admin area

Extracts the setting of the `admin` layout and verifying that users are admins
to a common base class for the admin/ controllers.

* Add basic coverage for admin/reports and admin/settings controllers