Support only federating Notes

When setting `notes_only = true` in the `[app]` configuration section, WF will only send out `Note` objects. Otherwise, it will send out both `Note`s and `Article`s.

config/config.go

@@ -140,6 +140,7 @@ type (
 		// Federation
 		Federation  bool `ini:"federation"`
 		PublicStats bool `ini:"public_stats"`
+		NotesOnly   bool `ini:"notes_only"`
 
 		// Access
 		Private bool `ini:"private"`

posts.go

@@ -1133,7 +1133,7 @@ func (p *PublicPost) CanonicalURL(hostName string) string {
 func (p *PublicPost) ActivityObject(app *App) *activitystreams.Object {
 	cfg := app.cfg
 	var o *activitystreams.Object
-	if strings.Index(p.Content, "\n\n") == -1 {
+	if cfg.App.NotesOnly || strings.Index(p.Content, "\n\n") == -1 {
 		o = activitystreams.NewNoteObject()
 	} else {
 		o = activitystreams.NewArticleObject()