[API] detect changes in the list of admins

[jbygdell]

Describe the bug
Since the file containing the list of admins can be updated outside of the deployment manifests (helm chart or other) the file needs to be watched i order to trigger a reload.
Steps to reproduce

Expected behavior

• detect changes in the file with admin user and trigger a config reload.
• Tests verifying the fix are added

Additional context

Estimation of size: small/medium/big

Estimation of priority: low/medium/high