Fix workflow nuxeo-document-task to include the case of assignment to a group

In https://github.com/nuxeo/nuxeo-web-ui/blob/release-10.10-HF44/elements/workflow/nuxeo-document-task.html#L138-L146 , you can notice that

type="user"

is forced, while a task can be assigned to group.

How to reproduce:

• Login as Administrator on https://nightly.nuxeo.com
• Start e.g. a serial workflow
• Enter in task assignment step the group members and start the review
• Possibly you then have to login as a members's member
• Select the task assigned and notice that
  • In Users in this task, the tag members can be clicked on
    • Click on members => You are directed to https://nightly.nuxeo.com/nuxeo/ui/#!/admin/user-group-management/user/members instead of https://nightly.nuxeo.com/nuxeo/ui/#!/admin/user-group-management/group/members ==> BREAKS as HTTP 404 !
  • In Participants, the tag group:members can be clicked on
    • Click on group:members => You are directed to https://nightly.nuxeo.com/nuxeo/ui/#!/admin/user-group-management/user/group%3Amembers instead of
      https://nightly.nuxeo.com/nuxeo/ui/#!/admin/user-group-management/group/members ==> BREAKS as HTTP 404 !

Request: the tags (representing participants and users in the task), when dealing with groups of users, should redirect correctly to the group page , instead of assuming and forcing users.