AccountExternalIdInfo: Add implementation of toString

Having a toString method with a readable representation of the object's
internal values makes it easier to diagnose problems when an assertion
about the object fails and dumps a stack trace.

Change-Id: I491f4cf79f53affd0afb4eb4b2fea7c016d76036
diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/AccountExternalIdInfo.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/AccountExternalIdInfo.java
index 9c64fd0..9e6770b 100644
--- a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/AccountExternalIdInfo.java
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/AccountExternalIdInfo.java
@@ -14,6 +14,8 @@
 
 package com.google.gerrit.extensions.common;
 
+import static com.google.common.base.MoreObjects.toStringHelper;
+
 import com.google.common.collect.ComparisonChain;
 import java.util.Objects;
 
@@ -47,4 +49,14 @@
   public int hashCode() {
     return Objects.hash(identity, emailAddress, trusted, canDelete);
   }
+
+  @Override
+  public String toString() {
+    return toStringHelper(this)
+        .add("identity", identity)
+        .add("emailAddress", emailAddress)
+        .add("trusted", trusted)
+        .add("canDelete", canDelete)
+        .toString();
+  }
 }