Add a Register link when using LDAP authentication

If auth.type is LDAP Gerrit is responsible for collecting the username
and password and authenticating to the directory.  But we don't have a
way to create new users in the directory, as this is far beyond any
scope we want to handle.

Site administrators might have a URL users can visit to create their
own account, or maybe just want to publish a mailto: link so the user
can request an account to be manually created for them.  Allow those
links to be configured through gerrit.config as auth.registerUrl.

Change-Id: I996ed53c5b80579f3a60cfcf9aebb7940d501366
Signed-off-by: Shawn O. Pearce <sop@google.com>

gerrit-common/src/main/java/com/google/gerrit/common/data/GerritConfig.java

@@ -23,7 +23,7 @@ import java.util.List;
 import java.util.Set;
 
 public class GerritConfig implements Cloneable {
-  protected String canonicalUrl;
+  protected String registerUrl;
   protected GitwebLink gitweb;
   protected boolean useContributorAgreements;
   protected boolean useContactInfo;
@@ -37,12 +37,12 @@ public class GerritConfig implements Cloneable {
   protected Set<Account.FieldName> editableAccountFields;
   protected List<RegexFindReplace> commentLinks;
 
-  public String getCanonicalUrl() {
-    return canonicalUrl;
+  public String getRegisterUrl() {
+    return registerUrl;
   }
 
-  public void setCanonicalUrl(final String u) {
-    canonicalUrl = u;
+  public void setRegisterUrl(final String u) {
+    registerUrl = u;
   }
 
   public AuthType getAuthType() {