Missing permissions attribute on repository collaborators and teams' repositories calls

[ryangribble]

I was writing a script to pull some auditing information from our github enterprise server when I stumbled into this one today. We are missing the permissions section of the response on repository collaborators and team repositories, which indicates the admin/push/pull permissions.

Here are the items I found so far that have the permissions attribute. It's also worth noting that this was in API preview mode and required a custom accept header until just recently when the preview period ended. In terms of GitHub Enterprise, on 2.5.x it is still preview, but is no longer preview on 2.6.x. So depending on whether our intention is to only support the latest feature build of GHE or whether we are also trying to support 2.5.x, we might want to specify that accepts header for these calls...

This is also somewhat related to #1101 where a new permission parameter (a single string/permission, rather than the permissions structure mentioned i this issue) can be provided when adding a collaborator to a repo, to denote what level of access they have.

List repository collaborators

{
"login": "octocat",
"id": 1,
"avatar_url": "https://github.com/images/error/octocat_happy.gif",
...
"type": "User",
"site_admin": false,
"permissions": {
"pull": true,
"push": true,
"admin": false
}

I also found other places where this appears such as

List team's repositories

{
"id": 1296269,
"owner": {
"login": "octocat",
"id": 1,
...
"type": "User",
"site_admin": false
},
"name": "Hello-World",
"full_name": "octocat/Hello-World",
...
"pushed_at": "2011-01-26T19:06:43Z",
"created_at": "2011-01-26T19:01:12Z",
"updated_at": "2011-01-26T19:14:43Z",
"permissions": {
"admin": false,
"push": false,
"pull": true
}

Also there is a custom accept header version of the Check teams access to repository which can return the full repository information (including the permissions attributes) rather than just the 204/404 response indicating true/false. Potentially we could implement this alongside the Task<bool> IsRepositoryManagedByTeam() call, to be a similar call but returning a Task<Repository> object