Make fields that are only initialized once final

roles/keycloak/files/providers/keycloak-mailpass-rest/src/main/java/org/archlinux/keycloak/mailpass/rest/MailPassResourceProvider.java

@@ -9,9 +9,9 @@ import org.keycloak.services.resource.RealmResourceProvider;
  */
 public class MailPassResourceProvider implements RealmResourceProvider {
 
-  private KeycloakSession session;
-  private String realmName;
-  private String realmRole;
+  private final KeycloakSession session;
+  private final String realmName;
+  private final String realmRole;
 
   /**
    * Store the pre-configured SPI fields to enable verification before requests take place.