update model validation event messages

runtime/model-avro/src/main/java/io/aklivity/zilla/runtime/model/avro/internal/AvroModelEventFormatter.java

@@ -26,7 +26,7 @@
 public final class AvroModelEventFormatter implements EventFormatterSpi
 {
     private final EventFW eventRO = new EventFW();
-    private final AvroModelEventExFW jsonModelEventExFW = new AvroModelEventExFW();
+    private final AvroModelEventExFW avroModelEventExFW = new AvroModelEventExFW();
 
     AvroModelEventFormatter(
         Configuration config)
@@ -39,15 +39,15 @@ public String format(
         int length)
     {
         final EventFW event = eventRO.wrap(buffer, index, index + length);
-        final AvroModelEventExFW extension = jsonModelEventExFW
+        final AvroModelEventExFW extension = avroModelEventExFW
             .wrap(event.extension().buffer(), event.extension().offset(), event.extension().limit());
         String result = null;
         switch (extension.kind())
         {
         case VALIDATION_FAILED:
         {
             AvroModelValidationFailedExFW ex = extension.validationFailed();
-            result = String.format("%s", asString(ex.error()));
+            result = String.format("A message payload failed validation. %s.", asString(ex.error()));
             break;
         }
         }

runtime/model-core/src/main/java/io/aklivity/zilla/runtime/model/core/internal/CoreModelEventFormatter.java

@@ -47,7 +47,10 @@ public String format(
         case VALIDATION_FAILED:
         {
             CoreModelValidationFailedExFW ex = extension.validationFailed();
-            result = String.format("%s", asString(ex.error()));
+            result = String.format(
+                    "A message payload failed validation. A field was not the expected type (%s).",
+                    asString(ex.error())
+            );
             break;
         }
         }

runtime/model-json/src/main/java/io/aklivity/zilla/runtime/model/json/internal/JsonModelEventFormatter.java

@@ -47,7 +47,7 @@ public String format(
         case VALIDATION_FAILED:
         {
             JsonModelValidationFailedExFW ex = extension.validationFailed();
-            result = String.format("%s", asString(ex.error()));
+            result = String.format("A message payload failed validation. %s.", asString(ex.error()));
             break;
         }
         }

runtime/model-protobuf/src/main/java/io/aklivity/zilla/runtime/model/protobuf/internal/ProtobufModelEventFormatter.java

@@ -47,7 +47,7 @@ public String format(
         case VALIDATION_FAILED:
         {
             ProtobufModelValidationFailedExFW ex = extension.validationFailed();
-            result = String.format("%s", asString(ex.error()));
+            result = String.format("A message payload failed validation. %s.", asString(ex.error()));
             break;
         }
         }

specs/model-avro.spec/src/main/scripts/io/aklivity/zilla/specs/model/avro/config/event.yaml

@@ -24,7 +24,7 @@ telemetry:
           - qname: test.net0
             id: model.avro.validation.failed
             name: MODEL_AVRO_VALIDATION_FAILED
-            message: java.io.EOFException
+            message: A message payload failed validation. java.io.EOFException.
 catalogs:
   test0:
     type: test

specs/model-core.spec/src/main/scripts/io/aklivity/zilla/specs/model/core/config/event.yaml

@@ -24,7 +24,7 @@ telemetry:
           - qname: test.net0
             id: model.core.validation.failed
             name: MODEL_CORE_VALIDATION_FAILED
-            message: string
+            message: A message payload failed validation. A field was not the expected type (string).
 bindings:
   net0:
     kind: server

specs/model-json.spec/src/main/scripts/io/aklivity/zilla/specs/model/json/config/event.yaml

@@ -24,7 +24,7 @@ telemetry:
           - qname: test.net0
             id: model.json.validation.failed
             name: MODEL_JSON_VALIDATION_FAILED
-            message: "[1,10][/id] The value must be of string type, but actual type is integer."
+            message: A message payload failed validation. [1,10][/id] The value must be of string type, but actual type is integer.
 catalogs:
   test0:
     type: test

specs/model-protobuf.spec/src/main/scripts/io/aklivity/zilla/specs/model/protobuf/config/event.yaml

@@ -24,7 +24,7 @@ telemetry:
           - qname: test.net0
             id: model.protobuf.validation.failed
             name: MODEL_PROTOBUF_VALIDATION_FAILED
-            message: "Cannot find field: date in message example"
+            message: "A message payload failed validation. Cannot find field: date in message example."
 catalogs:
   test0:
     type: test