refactor!: Move Base AuthClient Types to authclient.ts

[danielbankhead]

Today, there are types imported from other AuthClients that should be in the base client's file. E.g.:

google-auth-library-nodejs/src/auth/authclient.ts

Line 20 in f45f975

import {GetAccessTokenResponse, Headers} from './oauth2client';

These should be moved here and the imports should be updated throughout the codebase accordingly.

Implementation Notes:

• Ensure any top-level exports in src/index.ts work seamlessly

[HubertJan]

Hi @danielbankhead, I'd like to work on that.

Which other types should be moved to authclient.ts? At the moment, only GetAccessTokenResponse and Headers are directly imported from oauth2client.

[danielbankhead]

Thanks!

At the moment, only GetAccessTokenResponse and Headers are directly imported from oauth2client.

Today, only those two types should be moved. As this functionality will not be released until the next major release, it's left intentionally open in case a type slips through in the meantime.