fix: ConnectionMiddleware and IEnumerable + IConnection

[benmccallum]

Don't assume an IEnumerable/IQueryable isn't already an IConnection

[michaelstaib]

We should write one test to prove that it works.

[michaelstaib]

I will have to look at the new implementation so that this will work with 11 as well.

[benmccallum]

Added a unit test for this scenario (checked without my fix and the test failed as I was seeing, so that's a good sign :P).

I'm not too clued up on the other scenarios, which don't currently have unit tests, so perhaps you'd want to quickly bang out some of those for the other types the middleware can handle (like IQueryable, IEnumerable that's not an IConnection, etc.)? Added basic coverage.

I'm just wondering one thing. Should the IConnection scenario check inside to make sure that the Edge<T>, that T is TEntity? I'm thinking not, as it's more flexibile. Essentially we're saying if you're returning an IConnection, you know what you're doing and we'll take it as is. e.g. in my case I'm returning an IConnection of Supplier, but the field is typed as a connection of SupplierResult (a union that includes supplier) as I have middleware that swaps out supplier's for GoneSupplier when the supplier has left our platform as the user isn't an admin.

[benmccallum]

Added basic coverage of IQueryable and IEnumerable scenarios.