garm-server urls needs to be configured via API

[bavarianbidi]

What is the feature you would like to have?

With the upcoming garm version it's mandatory, that values for callback_url, metadata_url and webhooks_url are set during the initialization process.
ATM, these values are set in the garm-server configuration itself.

As initial step i propose to add these required values into the GarmServer struct:
https://github.com/mercedes-benz/garm-operator/blob/82e82aa8c3efb8dc147de91c7c9451120970f349/pkg/config/config.go#L20C1-L26C2

Afterwards we can abstract this configuration into a dedicated GarmServerCR

Anything else you would like to add?

Already implemented in garm with cloudbase/garm#256.

IIRC it's the only reason why the operator fails when it came to initializing a new garm-instance with version from main.
If this is implemented, all existing operator CRs should work again - but requires some manual interaction once #127 is implemented.