Fix acceptance

* Fix acceptance info API to return user_id
* Adjust the url sent in the role / license acceptance email
  ```
  Change the url to <webview.url>/contents/<id>@draft/role-acceptance

  MANUAL-UPGRADE: Add "webview.url" to the ini file (e.g. development.ini)
  ```
currently, we do content shadowing, so that webview doesn't have to know where to fetch content from. The nginx rules are:
location ~ ^/contents/.*@draft\.json {
           proxy_pass http://authoring:port;
       }
 
       location ~ ^/contents/.*@.*\.json {
           proxy_pass http://archive:port;
       }

I suppose I can add a rule to catch .*acceptance$ to make sure that goes to authoring.