Add flag to use webhooks and API call to register a hook

It almost works with webhooks now. Still TODO is:
* Remove the hook after the recording is published
* To process the publish_ended event from the webhooks either the webhook
  needs to include the metadata (currently it doesn't) or GreenLight has
  find out the meeting token without reading it from the metadata.

app/lib/bbb_api.rb

@@ -78,9 +78,13 @@ module BbbApi
           "meta_#{BbbApi::META_TOKEN}": meeting_token
         }
 
-        meeting_options.merge!(
-          { "meta_#{BbbApi::META_HOOK_URL}": options[:hook_url] }
-        ) if options[:hook_url]
+        if ENV['GREENLIGHT_USE_WEBHOOKS']
+          webhook_register(options[:hook_url], meeting_id)
+        else
+          meeting_options.merge!(
+            { "meta_#{BbbApi::META_HOOK_URL}": options[:hook_url] }
+          ) if options[:hook_url]
+        end
 
         # Create the meeting
         bbb.create_meeting(options[:meeting_name], meeting_id, meeting_options)
@@ -253,6 +257,26 @@ module BbbApi
     }
   end
 
+  def webhook_register(url, meeting_id=nil)
+    params = { callbackURL: url }
+    params.merge!({ meetingID: meeting_id }) if meeting_id.present?
+    bbb_safe_execute :send_api_request, "hooks/create", params
+  end
+
+  def webhook_remove(url)
+    res = bbb_safe_execute :send_api_request, "hooks/list"
+    if res && res[:hooks] && res[:hooks][:hook]
+      res[:hooks][:hook] = [res[:hooks][:hook]] unless res[:hooks][:hook].is_a?(Array)
+      hook = res[:hooks][:hook].select{ |h|
+        h[:callbackURL] == url
+      }.first
+      if hook.present?
+        params = { hookID: hook[:hookID] }
+        bbb_safe_execute :send_api_request, "hooks/destroy", params
+      end
+    end
+  end
+
   def success_join_res(join_url)
     {
       returncode: true,