Determine how to deal with multiple audiences for jwt.Credentials about google-auth-library-python

[dhermes]

1. I don't understand the "pretty awful performance-wise" piece you are referring to
2. I don't see much wrong with asking the caller to be aware of the audience. Libraries like google-cloud-python can handle this without being a burden on users.

[theacodes]

I don't understand the "pretty awful performance-wise" piece you are referring to

Generating a new JWT for every request adds a lot of overhead. It's much better to only generate that once.

I don't see much wrong with asking the caller to be aware of the audience.

Great, I'll do what I described in (2) above. I'll remove the per-request one-time JWT logic. We can always add that back as a new credential type later if needed, but if we hit 1.0 with that behavior we're married to it.