override equals and toString for ServoId

Helps make debugging easier.

spectator-reg-servo/src/main/java/com/netflix/spectator/servo/ServoId.java

@@ -23,7 +23,7 @@
 import java.util.Map;
 
 /** Id implementation for the servo registry. */
-class ServoId implements Id {
+final class ServoId implements Id {
 
   private final MonitorConfig config;
 
@@ -86,4 +86,24 @@ public void remove() {
     }
     return new ServoId(builder.build());
   }
+
+  @Override public boolean equals(Object obj) {
+    if (this == obj) return true;
+    if (obj == null || !(obj instanceof ServoId)) return false;
+    ServoId other = (ServoId) obj;
+    return config.equals(other.config);
+  }
+
+  @Override public int hashCode() {
+    return config.hashCode();
+  }
+
+  @Override public String toString() {
+    StringBuilder buf = new StringBuilder();
+    buf.append(config.getName());
+    for (com.netflix.servo.tag.Tag t : config.getTags()) {
+      buf.append(':').append(t.getKey()).append('=').append(t.getValue());
+    }
+    return buf.toString();
+  }
 }

spectator-reg-servo/src/test/java/com/netflix/spectator/servo/ServoIdTest.java

@@ -0,0 +1,40 @@
+/**
+ * Copyright 2015 Netflix, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.netflix.spectator.servo;
+
+import com.netflix.servo.tag.BasicTagList;
+import com.netflix.servo.tag.TagList;
+import nl.jqno.equalsverifier.EqualsVerifier;
+import nl.jqno.equalsverifier.Warning;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+
+@RunWith(JUnit4.class)
+public class ServoIdTest {
+
+  @Test
+  public void equalsContractTest() {
+    TagList ts1 = BasicTagList.of("k1", "v1");
+    TagList ts2 = BasicTagList.of("k1", "v1", "k2", "v2");
+    EqualsVerifier
+        .forClass(ServoId.class)
+        .withPrefabValues(TagList.class, ts1, ts2)
+        .suppress(Warning.NULL_FIELDS)
+        .verify();
+  }
+}