Create SAML generation route and controller

In order to take advantage of the new SAML generation code, we
need to create a route and controller in OS-FEDERATION.

corresponding api spec: https://review.openstack.org/#/c/113998/

Implements: bp keystone-to-keystone-federation

Change-Id: Ib27921fa1fcff8760836e065ede1e90d1330fd16
Merge "Create SAML generation route and controller"