Fixed badly formatted error messages in /api/fleet/orbit/device_token
endpoint and others.
In /api/fleet/orbit/device_token:
- Added token validation -- empty token not allowed
- Replaced 500 error with 409 when token conflicts with another host
#15832
# Checklist for submitter
If some of the following don't apply, delete the relevant line.
<!-- Note that API documentation changes are now addressed by the
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- [x] Changes file added for user-visible changes in `changes/` or
`orbit/changes/`.
See [Changes
files](https://fleetdm.com/docs/contributing/committing-changes#changes-files)
for more information.
- [x] Added/updated tests
- [x] Manual QA
Related to #7130, this adds logic to retry native notarization up to three times if it fails for some reason.
Since we're adding retries in various places, I added a new package under pkg for this purpose.