Related to https://github.com/fleetdm/fleet/issues/9588, we now handle 4xx responses from the fleetdm.com server and forward those to the client.
At the time of this commit, the only 4xx response that wasn't already handled by the server is because of an invalid email domain, so we assume that, but we should look into establishing a pattern of error messages with the website instead.
**Use nano's multi service**
This allows us to integrate more seamlessly with nano and to run our
custom MDM logic _after_ the request was handled by nano, which gives us
more flexibility (for example: now we can issue commands after a
TokenUpdate message)
From nano's code:
> MultiService executes multiple services for the same service calls.
> The first service returns values or errors to the caller. We give the
> first service a chance to alter any 'core' request data (say, the
> Enrollment ID) by waiting for it to finish then we run the remaining
> services' calls in parallel.
**Integration tests + fixes**
- Move some of the service logic from `cmd/` to `server/service`
- Add integration tests for the MDM enrollment flow, including SCEP
authentication.
- Fixed a bug that set `host_mdm.mdm_id = 0` during MDM enrollment due
to how MySQL reports the last insert id when `ON DUPLICATE KEY` is
used.
- Completely remove the host row from `host_mdm` when a device is
unenrolled from MDM to match the behavior of how we ingest MDM data
from osquery
Related to https://github.com/fleetdm/fleet/issues/8708,
https://github.com/fleetdm/fleet/issues/9034
