Fix federation documentation reference

The documentation for the federation extension referenced a class
that doesn't exist for the driver. Using the correct class name
will make it easier for deployers to configure federation.

bp identity-providers

Change-Id: I0f69d3465be78079a89e6d2c5e717aed04136a50
Fix docstrings in federation controller.

This fixes a couple of nits with the docstrings in the federation
controller.

bp identity-providers

Change-Id: I3db9478aaf02ac3ac5fb1e463baf014d7bb88975
Merge "Fix federation documentation reference"
Merge "Fix docstrings in federation controller."