Edit of resource policy miss ADD action and mandate the policy type

[abollini]

Describe the bug

It is not possible to manually add a resource policy with action type ADD to a community or a collection (it is missing in the dropdown).

Moreover, the resource policy type (TYPE_SUBMISSION, TYPE_WORKFLOW, etc.) is mandatory but it is not set by some policies created automatically by the system (submitters, administrators). This imply that if you try to edit such policies you are forced to provide a resource type name.

To Reproduce

Steps to reproduce the behavior:

1. login on the sandbox (the demo is currently unresponsive)
2. visit a community or collection
3. edit
4. go to the authorization tab
5. create a new Policy
6. check the mandatory fields and the values provided in the action types dropdown

Expected behavior

The ADD action type should be available. Resource type should be not mandatory, or we should introduce a SYSTEM_TYPE to be used in place of "null" for all the policies created automatically by the system