Hasura should emit codegen files

Hello all,

Today I find Hasura action's highly impratical in term of integration with TypeScript.

The codegen tab is a good idea, but why stop there and make people copy/paste code? It would be way better to emit at least the hasuraCustomTypes.ts file so we can directly import it and it becomes a reliable artefact. The console could just reflect changes to this file anytime we use the UI the modify the actions, and without touching anything else we would know that we broke our handler.

Start by tracing the Actions codegen tab and the Hasura console flow that modifies actions. Determine where the generated hasuraCustomTypes.ts content is assembled and how console changes are persisted. Done means the console emits that file as a reliable artefact and keeps it updated when actions are changed through the UI.

Written by the indexing model from the issue text.