some polishment of the provider API

[avodonosov]

See the suggestions here:

​http://lists.common-lisp.net/pipermail/cl-openid-devel/2008-September/000097.html

[avodonosov]

The changes implemented:

• HANDLE-OPENID-PROVIDER-REQUEST always returns the second value, an HTTP code. When the HTTP code is redirect (3xx), the first value URI is returned as a string, instead of a PURI:URI object. This saves user from doing PRINC-TO-STRING for the URI.

• CANCEL-RESPONSE and SUCCESSFUL-RESPONSE are renamed to CANCEL-RESPONSE-URI and SUCCESSFUL-RESPONSE-URI. Both functions return only single value - the URI (no sense to return the HTTP status code as the second value, as this is always recirect). The URI is returned as a string instead of PURI:URI instance.

• Removed WITH-INDIRECT-ERROR-HANDLER and SIGNAL-INDIRECT-ERROR from the public API.

• Introduced new public function AUTH-REQUEST-REALM with returns the realm of the OpenID authentication request message.

• The HANDLE-OPENID-PROVIDER-REQUEST keyword parameter SECURE-P is renamed to ALLOW-UNENCRYPTED-ASSOCIATION-P.

• Some adjustments in the docs.