**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
