Adding missing API endpoints

[Ente]

I've added the missing API endpoints.

Added endpoint groups:

• Address Rewriting
• DKIM (as requested in Feature Request: Get DKIM Key #2)
• oAuth2
• TLS Policy Maps
• Status
• Routing
• Resources
• Ratelimits
• Queue Manager
• Quarantine
• Forwarding Hosts
• Fail2Ban
• DomainAdmin
• App Passwords

I've also added some code documentation where I thought it would be useful. Some changes at the composer were also made.
My IDE had a problem with the autoloader as the MailCowAPI class has a different namespace which is not covered by the psr-4 autoloader. TL;DR: I've added the following lines within the "autoload" configuration:

       "files": ["src/MailCowAPI.php", "src/Credentials.php"],
        "classmap": ["src"]

And changing the use of Exbil\Mailcow\MailCowAPI to Exbil\MailCowAPI the other uses stay the same, like Exbil\Mailcow\Domains\Domains. Couldn't find any issues with targeted version or higher (PHP 8.2) and composer 2.7.7