Multiple single sign on (SSO) with the same provider (.registerService())

So the idea is to get access tokens for api for multiple entities from the same provider rather than basic SSO. I obviously could just pass in refresh token as top level field into return object of OAuth.registerService, but then I wouldn’t be able to use indexes if looking for account by refresh token, so how do I try and make array with register service method (which isn’t documented, I only assume that it is meteor package since it interfaces with accounts package), or try and make OAuth work if it is in fact used for actual SSO while using some callback to rearrange data so that I could have some field array that would let me find user._id by some service data.

I imagine I could try indexing against top level field holding refresh tokens, and seeing if index runs for exists operation, most likely creating a separate field with options, just so that I won’t have update index all that often using access tokens and such.

Actually index for embeded document doesnt support exist query.

Modified accounts method for external service, since I don’t think callback params would exactly enable this functionality, and still there’re packages that appear to let you modify previous and new account when adding SSO which works for same SSO if only for API access.