openid_verify(+Options, 
+Request)Handle the initial login form presented to the user by the relying party 
(consumer). This predicate discovers the OpenID server, associates 
itself with this server and redirects the user's browser to the OpenID 
server, providing the extra openid.X name-value pairs. Options 
is, against the conventions, placed in front of the Request 
to allow for smooth cooperation with http_dispatch.pl. Options 
processes:
- return_to(+URL)
 - Specifies where the OpenID provider should return to. Normally, that is 
the current location.
 
- trust_root(+URL)
 - Specifies the 
openid.trust_root attribute. Defaults to the 
root of the current server (i.e., http://host[.port]/). 
- realm(+URL)
 - Specifies the 
openid.realm attribute. Default is the
trust_root. 
- ax(+Spec)
 - Request the exchange of additional attributes from the 
identity provider. See http_ax_attributes/2 
for details.
 
The OpenId server will redirect to the openid.return_to 
URL.
- throws
 http_reply(moved_temporary(Redirect))