REST endpoint for configured and supported WebAPI features

During last architecture call (11 Jan) there was a discussion, that it would be useful to have REST endpoint, which returns what features are supported by current instance of WebAPI. E.g. whether authentication is turned on / off, what authentication providers are configured and available, whether there are any Data sources with CDM v5.3 connected to the WebAPI and therefore whether it is reasonable to show payer_plan options in cohort builder (the ones which are only supported by v5.3 and at older models will just cause errors), etc. Because now we have to sync such things between back-end and front-end configuration, which is bad approach - no single source of truth.