Fix -Wswitch-default

Fix and enforce absence of such issues.

examples/client/lwm2mclient.c

@@ -831,6 +831,9 @@ static void prv_display_objects(lwm2m_context_t *lwm2mH, char *buffer, void *use
             case TEST_OBJECT_ID:
                 display_test_object(object);
                 break;
+            default:
+                fprintf(stdout, "unknown object ID: %" PRIu16 "\n", object->objID);
+                break;
             }
         }
     }

wakaama.cmake

@@ -130,6 +130,7 @@ add_compile_options(
     -Werror=incompatible-pointer-types
     -Werror=shadow
     -Werror=strict-prototypes
+    -Werror=switch-default
 )
 
 # The maximum buffer size that is provided for resource responses and must be respected due to the limited IP buffer.