feat: Support SOAP interface

[Byloth]

CMaNGOS comes with a SOAP interface that can be used to execute server commands remotely.
Here's a basic usage example: https://github.com/cmangos/mangos-tbc/blob/f0e5bdc4d1cf53ffeeb1142b5f7290b464b9984a/contrib/soap/example.php

As @viccroy stated on Discord, it can also be used to shutdown the server, allowing players to see the shutdown warning in-game.
This -of course- is just one of a possible use.

---

• Build the containers with this interface enabled (if needed).
• Expose the port (if needed).
• Make credentials configurable via environmental variables.
• ... other... ?