Implement OAuth2 Client Credentials Flow

[willi-mueller]

Feature description

the rest_client.auth should offer also OAuth2 Client Credentials authentication flow (two-legged flow).

Are you a dlt user?

Yes, I'm already a dlt user.

Use case

To authenticate to sources, such as Zoom.
This will be very useful to build rest_api sources.

Proposed solution

Implement a subclass to rest_api.auth.OAuth2AuthBase.

Related issues

No response