Added OAuth 2.0 classes

src/main/java/org/scribe/builder/api/DefaultApi20.java

@@ -1,15 +1,42 @@
 package org.scribe.builder.api;
 
-import org.scribe.model.OAuthConfig;
-import org.scribe.oauth.OAuthService;
+import org.scribe.model.*;
+import org.scribe.oauth.*;
 
-public class DefaultApi20 implements Api
+/**
+ * Default implementation of the OAuth protocol, version 2.0 (draft 11)
+ *
+ * This class is meant to be extended by concrete implementations of the API,
+ * providing the endpoints and endpoint-http-verbs.
+ *
+ * If your Api adheres to the 2.0 (draft 11) protocol correctly, you just need to extend
+ * this class and define the getters for your endpoints.
+ *
+ * If your Api does something a bit different, you can override the different
+ * extractors or services, in order to fine-tune the process. Please read the
+ * javadocs of the interfaces to get an idea of what to do.
+ *
+ * @author Diego Silveira
+ *
+ */
+public abstract class DefaultApi20 implements Api
 {
 
-  @Override
+  /**
+   * Returns the URL where you should redirect your users to authenticate
+   * your application.
+   *
+   * @param config OAuth 2.0 configuration param object
+   * @return the URL where you should redirect your users
+   */
+  public abstract String getAuthorizationUrl(OAuthConfig config);
+
+  /**
+   * {@inheritDoc}
+   */
   public OAuthService createService(OAuthConfig config, String scope)
   {
-    return null;
+    return new OAuth20ServiceImpl(this, config);
   }
 
 }