Cosmetic changes, smarter logging for Principal.NULL_PRINCIPAL

Author: artem-v

services-api/src/main/java/io/scalecube/services/RequestContext.java

@@ -185,7 +185,8 @@ public static Mono<RequestContext> deferSecured() {
                 if (LOGGER.isDebugEnabled()) {
                   LOGGER.debug(
                       "Insufficient permissions for secured method ({}): "
-                          + "request context does not have principal",
+                          + "request context ({}) does not have principal",
+                      context,
                       context.methodInfo());
                 }
                 throw new ForbiddenException("Insufficient permissions");

services-api/src/main/java/io/scalecube/services/auth/Principal.java

@@ -4,7 +4,13 @@
 
 public interface Principal {
 
-  Principal NULL_PRINCIPAL = new Principal() {};
+  Principal NULL_PRINCIPAL =
+      new Principal() {
+        @Override
+        public String toString() {
+          return "NULL_PRINCIPAL";
+        }
+      };
 
   default String role() {
     return null;

services-api/src/main/java/io/scalecube/services/methods/ServiceMethodInvoker.java

@@ -249,7 +249,9 @@ private Mono<Principal> mapPrincipal(RequestContext context) {
         if (LOGGER.isDebugEnabled()) {
           LOGGER.debug(
               "Insufficient permissions for secured method ({}): "
-                  + "request context does not have principal and principalMapper is also not set",
+                  + "request context ({}) does not have principal "
+                  + "and principalMapper is also not set",
+              context,
               methodInfo);
         }
         throw new ForbiddenException("Insufficient permissions");