Bug fixes

Fix isset issue on getMessages

Issue #2954663: Encrypt the xoxb- and xoxb- API tokens
Remove all deprecations
Other small coding tweaks

* Issue #3122628 by VladimirAus: PHPCS and upgrade status warnings fixes
* Issue #3009382 by VladimirAus, neclimdul: CSRF on delete url
* Issue #3117996 by neelam_wadhwani, VladimirAus: All dependencies must be prefixed with the project name
* Issue #3117989 by prabha1997, VladimirAus: Drupal 9: remove deprecated function calls
* Added tests, removed features context.
* Added code review suggestions.

Realised the URL to URI fix didn't make the last tag - whoops!

Fixed one small bug with the URI alter - wrong variable name passed.

Applied patches from: -