This PR adds a new category setting which is a column in the `categories` table, `allow_unlimited_owner_edits_on_first_post`.
What this does is:
* Inside the `can_edit_post?` method of `PostGuardian`, if the current user editing a post is the owner of the post, it is the first post, and the topic's category has `allow_unlimited_owner_edits_on_first_post`, then we bypass the check for `LimitedEdit#edit_time_limit_expired?` on that post.
* Also, similar to wiki topics, in `PostActionNotifier#after_create_post_revision` we send a notification to all users watching a topic when the OP is edited in a topic with the category setting `allow_unlimited_owner_edits_on_first_post` enabled.
This is useful for forums where there is a Marketplace or similar category, where topics are created and then updated indefinitely by the OP rather than the OP making new topics or additional replies. In a way this acts similar to a wiki that only one person can edit.
* REFACTOR: Rename SiteSetting.disable_edit_notifications to disable_system_edit_notifications
- The older name could cause some confusion because the setting does not disable all edit notifications, only system ones.
* FIX: Add frozen_string_literal: true in the migration
* DEV: Deprecate 'disable_edit_notifications'
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
* Add revision number to notification url
* Pop modal on route change
* Add semicolon
* Ensure modal pops even when navigating within a topic
* Ensure modal pops when visiting from other page
* Fix eslint errors
* Fix prettier errors
* Add callback for notification item click
* Remove stray revisionUrl function
* Rename to afterRouteComplete
Rails yanked out observers many many years ago, instead the functionality
was yanked out to a gem that is very lightly maintained.
For example: if we want to upgrade to rails 5 there is no published gem
Internally the usage of observers had quite a few problem.
The series of refactors renamed a bunch of classes to give us more clarity
and removed some magic.
