Fix groups' casing

Users and groups have a canonical casing that is not necessarily all
lower-case. OpenID provides the canonical casing for the user, but
groupId in Provisioning does not. Thus, we swap to using groupName which
has the correct casing and appending the domain manually.
diff --git a/src/com/google/enterprise/adaptor/googleauthn/GoogleAuthnAdaptor.java b/src/com/google/enterprise/adaptor/googleauthn/GoogleAuthnAdaptor.java
index 32dd282..b844dd6 100644
--- a/src/com/google/enterprise/adaptor/googleauthn/GoogleAuthnAdaptor.java
+++ b/src/com/google/enterprise/adaptor/googleauthn/GoogleAuthnAdaptor.java
@@ -194,7 +194,9 @@
       GenericFeed groupsFeed = groupService.retrieveGroups(username, true);
       while (groupsFeed != null) {
         for (GenericEntry entry : groupsFeed.getEntries()) {
-          groups.add(entry.getProperty("groupId"));
+          // Use groupName instead of groupId because groupName uses the group's
+          // canonical casing.
+          groups.add(entry.getProperty("groupName") + "@" + domain);
         }
         Link nextPage = groupsFeed.getNextLink();
         if (nextPage == null) {