View of table column with enum is not an enum in the API

### Is your proposal related to a problem?

Say I have a table which contains a text column with a foreign key to a Hasura enum table.

In the GraphQL API, Hasura strongly types the column with a GraphQL enum type.

Now, I create a view of that table with the same column type. The GraphQL API now unfortunately loosely types the column as `String`.

### Describe the solution you'd like

The type of the column in the GraphQL API of the view should reflect the type of the column in the underlying data. I understand the difficulty in doing this given Hasura's current design for enums -- but nevertheless, this is a significant problem with using views with Hasura and should be solved.

### Describe alternatives you've considered

There aren't any reasonable ones as far as I can tell.

Reproduce the reported schema with a table containing a Hasura enum-backed text column and a view exposing the same column. Start by examining how Hasura generates GraphQL types for the table and view; done means the view column is exposed with the same GraphQL enum type rather than String.

Written by the indexing model from the issue text.