Expose an api endpoint, which lists linked mappings/references of a source

[rkorytkowski]

It should be possible to determine, if a given source has content, which is referenced from other resources. It is basically about exposing a list similar to the one produced when trying to delete such a source.

[rkorytkowski]

@snyaggarwal is it implemented already?

[snyaggarwal]

@rkorytkowski Not yet!

[PatrickCmd]

@rkorytkowski @jamlung-ri @snyaggarwal is it possible to have a sample json of how this should be like.