Change UI to use new OAuth API/Protocol

[ChristopheDuong]

Tell us about the problem you're trying to solve

1. Following up on Add auth config to oauth api  #7798, the OAuth API endpoints are now changed to work with inputOAuthConfiguration objects when the oauth depends on values from connector.
2. Following up on Change protocol for new OAuth Spec #7827, the OAuth API endpoints are changed to have a better and clearer specifications of how outputs should be handled by the UI/server afterwards

Describe the solution you’d like

Adapt the Front-end code base to those new API/Protocols:

• When FE calls the completeOauth API endpoint, a auth config is built with values extracted from a partial connector config if any fields is used as input fields to the oauth flow
• once oauth flow is completed, the backend returns the oauth outputs inside the auth config. The Front-end would have to merge this config back to the connector config where it needs to (as declared in the rootObject in auth spec object).
• Once merged, FE can continue with the modified connectionConfig to SourceCreate when clicking on "setup connection"

[ChristopheDuong]

For the moment, this ticket is blocked by #7827 which is waiting for approval

[ChristopheDuong]

This is now unblocked and UI work can start interacting with the new API even if it's not completely implemented yet

(Missing #6971 to properly take into account the Input config object, but since, no connector publishes the new spec yet, it doesn't matter anyway)

[ChristopheDuong]

The full implementation is merged to master, let me know if you see anything wrong with the backend/api!

Thanks

[ChristopheDuong]

You will have an example of spec.json with new OAuth protocol here #7952 once that is published