[ADD] added rating, rating_project and rating_project_issue module

 - Task : https://www.odoo.com/web#id=8060&view_type=form&model=project.task
 - Pad : https://pad.odoo.com/p/r.2BmKqyvcwKbiXPRI

[IMP] Added option to install rating module under Project

[IMP] added template to display when customer rates the task/issue

[IMP] Improved template and code

[IMP] : rating , rating_project and rating_project_issue as per new api

[IMP]: rating template

[FIX] : test case failed

[IMP] : code
This will force the model having the field. If it has not, then you can call the method, and we will avoid traceback. In your case, template_res_is will be the stage_id.id, since you have one. For other cases, such as rating_product, or rating_livechat, the process will be different, but the mixin must propose multiple way to allow rating (throught an email, a link, ... for instance).