Principals from settings not taken into account when hiding permissions

[leplatrem]

Since #837, the permissions are empty if the user has no write permission.

But the permissions from settings are not taken into account.

For example, with this conf:

# kinto.ini
kinto.bucket_create_principals = system.Authenticated
kinto.bucket_write_principals = system.Authenticated

Someone creates a bucket:

$ http PUT :8888/v1/buckets/her --auth token:alice
HTTP/1.1 201 Created
Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff
Content-Length: 154
Content-Type: application/json; charset=UTF-8
Date: Fri, 28 Oct 2016 15:27:25 GMT
Etag: "1477668445792"
Last-Modified: Fri, 28 Oct 2016 15:27:25 GMT
Server: waitress

{
    "data": {
        "id": "her", 
        "last_modified": 1477668445792
    }, 
    "permissions": {
        "write": [
            "basicauth:a06c2d0d82a192b5afab7695eb1159b75dd5a7732caa442db624e5c7c334bcb6"
        ]
    }
}

Because of the setting, every can write. However:

$ http GET :8888/v1/buckets/her --auth token:bob  
HTTP/1.1 200 OK
Access-Control-Expose-Headers: Content-Length, Expires, Alert, Retry-After, Last-Modified, ETag, Pragma, Cache-Control, Backoff
Cache-Control: no-cache, no-store
Content-Length: 68
Content-Type: application/json; charset=UTF-8
Date: Fri, 28 Oct 2016 15:27:35 GMT
Etag: "1477668445792"
Last-Modified: Fri, 28 Oct 2016 15:27:25 GMT
Server: waitress

{
    "data": {
        "id": "her", 
        "last_modified": 1477668445792
    }, 
    "permissions": {}
}

Once bob touches the object, a write permission is added, and he can see the permissions:

$ http PUT :8888/v1/buckets/her --auth token:bob

Then only he can see them:

$ http GET :8888/v1/buckets/her --auth token:bob
HTTP/1.1 200 OK
Access-Control-Expose-Headers: Content-Length, Expires, Alert, Retry-After, Last-Modified, ETag, Pragma, Cache-Control, Backoff
Cache-Control: no-cache, no-store
Content-Length: 231
Content-Type: application/json; charset=UTF-8
Date: Fri, 28 Oct 2016 15:32:24 GMT
Etag: "1477668710206"
Last-Modified: Fri, 28 Oct 2016 15:31:50 GMT
Server: waitress

{
    "data": {
        "id": "her", 
        "last_modified": 1477668710206
    }, 
    "permissions": {
        "write": [
            "basicauth:a06c2d0d82a192b5afab7695eb1159b75dd5a7732caa442db624e5c7c334bcb6", 
            "basicauth:5b3d8c06ef1c659316610d3be9cf5147ca56906d9dd1d6e1d678176843da40e6"
        ]
    }
}

The principals specified in the settings must be taken into account when hiding permissions.

Related #893 #837 #350

[leplatrem]

Related #892