Add a function that will check if a `campari` lc already exists for a given provenance id/tag process etc.

[ColeFMeldorf]

per a slack conversation:

"We need to add a function that will query the database for "all objects under provenance X that do not yet have a campari lightcurve under provenance Y", where X and Y can be specified either by provenance id, or by provenance tag and process."
-Rob