File access request API

[bappun]

Through the API, being able to:

• list access requests for a file
• grant access to a file for a specific user
• deny access to a file for a specific user

I think it could be also great to have an API to list all requests inside a dataverse, a dataset and maybe for all the files of a user (all files for which he has permission to manage requests).

Dataverse Community discussion: https://groups.google.com/forum/#!topic/dataverse-community/PY7uz6cg8vQ

[djbrooke]

We should build the ability to request access for a file using the API as part of this as well.

[pdurbin]

I left a review on pull request #5309 and discussed it with @sekmiller who is going to make a few tweaks.

I was pleased to see at least a partial fix for #2855 in there (that issue is not a "small chunk" issue). As I explained at #2855 (comment) currently the person receiving the "access has been requested" email gets no indication of who is requesting the file. It looks like this: