thinktecture/Thinktecture.IdentityModel — pull request #55 by ShannonKasperNoesis (2014-09-04 18:15:46+00:00)
Title: Change AddHeader method to append header value if one already exists

Use Owin AppendValues helper method to append a header value if a value already exists. It's needed if another owin middleware has already set the WWW-Authenticate header.