IDM-11: Use a community identity for InCommon authentication

Executive Summary: 
A community member needs to authenticate to a service that accepts InCommon authentication.
User Importance Summary: 
Access to resources and services in the public research computing community requires persistent identities for individuals. Some community members aren't affiliated with InCommon-participating institutions (e.g., non-R01 institutions are rarely InCommon participants), so this use case allows them to use their community identity to authenticate to services that require InCommon authentication.
Target Communities and Sizes: 
Community members at institutions that don't participate in InCommon or eduGAIN - 100 < N < 1,000