mod_http_oauth2: Separate extracting credentials from requests and verifying The token endpoint also uses Basic auth, but the password would be the client_secret, so we need to verify against that instead of using test_password(). Splitting this up here avoids code duplication. Possibly this new function could go into util.http...

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

``` sh
prosodyctl mod_listusers
```