Apply Mentions everywhere (#595)

* variables and mentions

* fix lint

* add missing changes

* fix tests

* update quilly, fix bugs

* fix lint

* apply fixes

* apply fixes

* Fix MentionParser

* Apply Mentions everywhere

* Fix MentionParserTest

* Small refactoring

* Fixing quill import issues

* Polished email integration, added customer sender mail

* Add missing changes

* improve migration command

---------

Co-authored-by: Frank <csskfaves@gmail.com>
Co-authored-by: Julien Nahum <julien@nahum.net>

api/resources/data/forms/integrations.json

@@ -7,13 +7,6 @@
     "is_pro": false,
     "crisp_help_page_slug": "can-i-receive-notifications-on-form-submissions-134svqv"
   },
-  "submission_confirmation": {
-    "name": "Submission Confirmation",
-    "icon": "heroicons:paper-airplane-20-solid",
-    "section_name": "Notifications",
-    "file_name": "SubmissionConfirmationIntegration",
-    "is_pro": true
-  },
   "slack": {
     "name": "Slack Notification",
     "icon": "mdi:slack",