Allow use of query strings in redirect_uri

[l-hedgehog]

The validation introduced in #534 make it an error.

[rfk]

For our reference, The Spec explicitly allows this:

   The redirection endpoint URI MUST be an absolute URI as defined by
   [RFC3986] Section 4.3.  The endpoint URI MAY include an
   "application/x-www-form-urlencoded" formatted (per Appendix B) query
   component ([RFC3986] Section 3.4), which MUST be retained when adding
   additional query parameters.  The endpoint URI MUST NOT include a
   fragment component.