Implement domains api

[ThomasRedpanda]

BaseKit api documentation https://git.sandwave.io/sandwave/relapp/-/merge_requests/504

Module

• Add a DomainsApi in the Api namespace.
• Add a DomainsApiInterface in the Api/Interfaces namespace.
• Add the module to the BaseKit class.

Endpoints

• Map domain
• Unmap domain

When implementing the endpoints, make sure to include links to the documentation using the @see annotation in docblocks.

Testing

• Add the module to the BaseKitClientTest to make sure it gets implemented.
• Add tests for all the added domain objects
• Add tests for all the added endpoints