[FEATURE] sanity check endpoints for each service

[robyj]

Hi

After spending far too long trying to get an islandora system to work correctly, I realized that it'd be nice if each of the services had a "sanity-check" endpoint, so admins/developers could check to see if the service is running correctly.

I'm not sure what it would look like, whether it'd just be a simple "Ok" returned or it would return some information to see if any prerequisites (say, ffmpeg for Homarus, a valid connection back to tomcat for Milliner) can be found. I think it'd make peoples lives easier

Thanks
Jon

[DonRichards]

I started down this by means of using a bash script to check. Problem for me is this isn't complete but it's compiled from feedback I received from people in the community. https://gist.github.com/DonRichards/cf3334218abdd23601564d600f55e94a