[User] Prepare User extension #1

Goal

Prepare User Extension (ext-user) and move the "User" bounded context from the "domain" repository.

Dependencies

• ext-base
• dev-tools - dev
• phpunit - dev
• faker - dev
• phpat - dev
• security-advisories - dev

Acceptance Criteria

• All the "User" bounded context files from the "domain" repository should be moved to "ext-user" src folder
• All the tests files related to "User" bounded context files from the "domain" repository should be moved to "ext-user" test folder
• PHPStan implemented and level 8 passes
• PHPAt architecture test should be added and passes
• PHP CS Fixer implemented and should be fixed any invalid code format