mod_http_oauth2: Add a special "xmpp" scope that grants the users' default role This will be the first step towards defining a standard set of XMPP scopes. "xmpp" behaves as an alias for the user's default role, so that the client does not need to know about the various prosody:* roles.

Removes invalid characters from roster entries.

```bash
sudo prosodyctl mod_clean_roster
```