fix: add method_exists check before calling method and replace security with encryption

See merge request !6

- Removed inputs for 'quiqqer-major-version' from .gitlab-ci.yml file for stabilization.
- Allowed phpunit to run on PHP 8.1 by removing phpunit-php8.1 block from .gitlab-ci.yml.
- Updated the homepage URL from 'http' to 'https' in composer.json.
- Changed the support URL from 'http' to 'https' in composer.json.
- Updated the required 'quiqqer/quiqqer' version to 'quiqqer/core' '^2' in composer.json.

BREAKING CHANGE: 'quiqqer/quiqqer' version to 'quiqqer/core'

In this commit, added an existence check before calling the checkEditPermission method in ajax
files. The Security class use in some files was replaced by Encryption. This commit also made
adjustment on getUser function to either return user object or null.

Related: #4

Update 'next-2.x' with latest changes from 'main'

See merge request !5

Next 1.x

See merge request !4

Add QUIQQER Tooling

See merge request !3

Next

See merge request !2

feat: new versioning

See merge request !1