make NotificationRecipient a little more customizable

app/models/notification_recipient.rb

@@ -5,12 +5,18 @@ class NotificationRecipient
     custom_action: nil,
     target: nil,
     acting_user: nil,
-    project: nil
+    project: nil,
+    group: nil
   )
+    unless NotificationSetting.levels.key?(type) || type == :subscription
+      raise ArgumentError, "invalid type: #{type.inspect}"
+    end
+
     @custom_action = custom_action
     @acting_user = acting_user
     @target = target
-    @project = project || @target&.project
+    @project = project || default_project
+    @group = group || @project&.group
     @user = user
     @type = type
   end
@@ -111,12 +117,18 @@ class NotificationRecipient
       end
   end
 
+  def default_project
+    return nil if @target.nil?
+    return @target if @target.is_a?(Project)
+    return @target.project if @target.respond_to?(:project)
+  end
+
   def find_notification_setting
     project_setting = @project && user.notification_settings_for(@project)
 
     return project_setting unless project_setting.nil? || project_setting.global?
 
-    group_setting = @project&.group && user.notification_settings_for(@project.group)
+    group_setting = @group && user.notification_settings_for(@group)
 
     return group_setting unless group_setting.nil? || group_setting.global?