First attempt at OpenID login

See https://git.autonomic.zone/compose-stacks/mediawiki/issues/14.

LocalSettings.php.tmpl

@@ -183,6 +183,16 @@ $wgGroupPermissions['*']['createaccount'] = false;
 $wgDebugLogFile = "/var/log/debug-{$wgDBname}.log";
 {{ end }}
 
+{{ if eq (env "OPENID_ENABLED") "1" }}
+wfLoadExtension( 'PluggableAuth' );
+wfLoadExtension( 'OpenIDConnect' );
+
+$wgOpenIDConnect_Config['{{ env "OPENID_KEYCLOAK_URL" }}'] = [
+  'clientID' => '{{ env "OPENID_CLIENT_ID"}}',
+  'clientsecret' => '{{ secret "openid-client-secret" }}'
+];
+{{ end }}
+
 {{ if env "SMTP_HOST" }}
 $wgSMTP = [
     'host'     => '{{ env "SMTP_HOST" }}', // could also be an IP address. Where the SMTP server is located