Added method level comments and null checks in DCA

components/oauth-extensions/dynamic-client-manager/src/main/java/org/wso2/carbon/identity/oauth/extension/DynamicClientRegistrationUtil.java

@@ -228,6 +228,11 @@ public class DynamicClientRegistrationUtil {
             oAuthAdminService.removeOAuthApplicationData(consumerKey);
 
             ApplicationManagementService appMgtService = ApplicationManagementService.getInstance();
+
+            if (appMgtService == null) {
+                throw new APIManagementException("Error occurred while retrieving Application Management" +
+                        "Service");
+            }
             ServiceProvider createdServiceProvider = appMgtService.getApplication(applicationName);
 
             if (createdServiceProvider == null) {

components/oauth-extensions/dynamic-client-manager/src/main/java/org/wso2/carbon/identity/oauth/extension/RegistrationService.java

@@ -45,9 +45,24 @@ public interface RegistrationService {
         }
     }
 
+    /**
+     * This method is used to register an Oauth application.
+     *
+     * @param profile contains the necessary attributes that are
+     *                needed in order to register an app.
+     * @return Status 200 if success including consumerKey and consumerSecret.
+     */
     @POST
     Response register(RegistrationProfile profile);
 
+    /**
+     * This method is used to remove already registered Oauth application.
+     *
+     * @param applicationName name of the application.
+     * @param userId name of the application owner.
+     * @param consumerKey provided consumerKey for the registered application.
+     * @return Status 200 if success.
+     */
     @DELETE
     public Response unregister(@QueryParam("applicationName") String applicationName,
                                @QueryParam("userId") String userId,