This change adds a github registration endpoint that instances can use
to fetch a github registration token.
This change also invalidates disables access to an instance to the token
and status updates endpoints once the instance transitions from
"pending" or "installing" to any other state.
Runners can now be manually removed using the CLI. Some restrictions apply:
* A runner must be idle in github. Github will not allow us to remove a runner
that is running a workflow.
* The runner status must be "running"
Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>
