An introspective metadata endpoint

[CasperWA]

It would be great to have an introspective metadata endpoint, like /about or /info to retrieve all relevant metadata useful for debugging.
This could include:

• OTEAPI-services version.
• OTEAPI Core version.
• List of installed OTEAPI plugins.
• List of installed OTEAPI plugin versions.
• List of endpoint paths/routes.
• Full list of (non secret) configuration settings.
• Redis instance information.
• ...

[quaat]

Regarding exposing the metadata - we need to ensure this information should not be publicly available. Knowing which versions of dependent libraries are running can be useful info for people with harmful intents. If we create an admin/ -endpoint and encourage not to publicly expose it, we can use this for extracting metadata, statistics, etc...