Remove login dialogs and replace with /login/ URLs

Insetad of handling OpenID and username/password authentication in
the GWT UI redirect all forms of authentication through /login/.

This allows the server to return normal HTML to handle the user
sign-in process. By using typical form based HTML for username
and password login browsers can offer the choice to save this
data locally in the user's password store.

Using /login/ for all authentication simplifies some UI code and
may make things easier for plugins.  A plugin only needs to do a
redirect to /login/ to upgrade an anonymous user to be an
authenticated one.

Change-Id: I0d7a59693a257c5da8bab19e3ef0a627f8a41c6e

gerrit-server/src/main/java/com/google/gerrit/server/auth/openid/OpenIdProviderPattern.java

@@ -0,0 +1,45 @@
+// Copyright (C) 2009 The Android Open Source Project
+//
+// 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.google.gerrit.server.auth.openid;
+
+import com.google.gerrit.reviewdb.client.AccountExternalId;
+
+public class OpenIdProviderPattern {
+  public static OpenIdProviderPattern create(String pattern) {
+    OpenIdProviderPattern r = new OpenIdProviderPattern();
+    r.regex = pattern.startsWith("^") && pattern.endsWith("$");
+    r.pattern = pattern;
+    return r;
+  }
+
+  protected boolean regex;
+  protected String pattern;
+
+  protected OpenIdProviderPattern() {
+  }
+
+  public boolean matches(String id) {
+    return regex ? id.matches(pattern) : id.startsWith(pattern);
+  }
+
+  public boolean matches(AccountExternalId id) {
+    return matches(id.getExternalId());
+  }
+
+  @Override
+  public String toString() {
+    return pattern;
+  }
+}