mod_http_oauth2: Fix treatment of 'redirect_uri' parameter in code flow It's optional and the one stored in the client registration should really be used instead. RFC 6749 says an URI provided as parameter MUST be validated against the stored one but does not say how. Given that the client needs their secret to proceed, it seems fine to leave this for later.

This module adds a command to `prosodyctl` for listing users.

``` sh
prosodyctl mod_listusers
```