[FEATURE] dry-run / test deployment

[JoernBerkefeld]

A new option for deploy should allow running deploy EXCEPT for the actual server interaction. That way, we get to see if deploy would have thrown errors without actually touching the server.

Ideally we combine that with a new --noCreate flag:
if --dryrun / --dr is set it is then similar to setting --noCreate and --noUpdate?

Would not work if the deployment creates new keys or changes existing keys required by following items. To handle that, we would need to fake the update in our cache.

Bit of a bigger task but could become quite the game changer also in collaboration with automatic runs in pull requests.

To make it work in the context of github actions one would need to create the auth file on the fly with secrets stored securely to allow caching things from the server. This part should be split off into a second ticket.