No access call when indirect subscription becomes direct

[jirenius]

Issue

Resgate does not make an access call on an indirectly subscribed resource after it turns to a solely directly subscribed resource.

Example

Let assume we have a resource test.parent with a resource reference to test.child:

• Client subscribes to test.parent and gets test.child as an indirectly subscribed resource.
• Client subscribes to test.child, which triggers no access request as it is also indirectly subscribed.
• Client unsubscribes to test.parent, which turns test.child to a solely directly subscribed resource.
• Resgate erroneously does not confirm client's access to test.child
• Service sends a reaccess on test.parent, and denies access.
• Client will continue to receive events for test.child even if access should have been revoked.

Impact

May have access control impact for solutions where reaccess is used on nested resources.

Solution

On unsubscribe, Resgate should check if any referenced resource is directly subscribed without any indirect reference. In such a case, Resgate should trigger a reaccess on the referenced resource.

[jirenius]

Fixed in #99