The duplicate entity check doesn't work transitively

[parsonsmatt]

So the fix in #1255 isn't quite enough. The tests in #1287 document the issue.

With the following format:

module A where
  
  mkPersist sqlSettings [persistLowerCase|
    A
      name Text
    |]

module B where

  import A
  mkPersistWith sqlSettings $(discoverEntities) [persistLowerCase|
    B
      a AId
  |]

module C where

  import B

  mkPersistWith sqlSettings $(discoverEntities) [persistLowerCase|
    C
      b BId
    |]

You'll get duplicate name errors because the mkPersistWith in C is trying to make models for A. A is not available for lookupTypeName, but it is still present in the input entity list.

Seems like it should be straightforward to just not generate things from the input list??