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 produces more detailed HTTP logs for Prosodys built-in HTTP
server. The format is similar to that of Apache and go into Prosodys
normal logs at the `info` level.