Code completion fails for OIDC connections

When the connection builder adds OIDC auth, it delegates to a separate OIDC builder. When the OIDC builder completes, it returns a reference to the original connection builder which was stored as an instance variable on the OIDC builder instance.

This works fine when executing the Python, however static type checking fails because the type of the connection builder is not fixed. The connection builder is generally sub-classed, and so the connection builder type cannot be hard coded. The current implementation hardcodes the base connection builder class, which is incorrect if the connection builder has been sub-classed. As a result, the type returned by the completion of the OIDC builder is incorrect, which breaks intellisense in both PyCharm and VS Code.

See #40 for more details.