OpenID spec violation. Extract Authentication data - *search* for OP Identifier element

Issue Summary

OpenID 2.0 Authentication 7.3.2.2. Extracting Authentication Data:

Once the Relying Party has obtained an XRDS document, it MUST first search the document (following the rules described in [XRI_Resolution_2.0]) for an OP Identifier Element. If none is found, the RP will search for a Claimed Identifier Element.

SO:

First, Drupal should search throught the XRDS document, trying to find whether it contains an OP Identifier element which is a Service element, containing a Type tag with the text content "http://specs.openid.net/auth/2.0/server" and a URI tag (the text content is the OP endpoint URL Drupal must use to do authentication requests).

If Drupal cannot find this OP Identifier element, it should try to find a Claimed Identifier Element which is a Service element, containing a Type tag with the text content http://specs.openid.net/auth/2.0/signon", a URI tag (containing the OP endpoint URL as above) and an optional LocalID tag (an identifier used by the OpenID provider to identify the user).

This issue is brought to you by the OpenID 2.0 Compliance Crusade