refactor indexer management API layer

[saihaj]

Summary
Rework the indexer-common GraphQL API layer to utilize GraphQL Codegen Server preset with GraphQL Yoga.

Background
When I was working on #858 I noticed that to create new resolver we update the SDL and then manually type out everything. When I was trying to write unit tests there was some bug which was causing my writes to be not written to DB. The setup is uncommon and debugging was just painful. This PR attempts to do something to reduce the pain

What does this PR change?

1. Brings in code generation
   • Instead of typing manually we utilize code generation
   • Simplify the DB models typings
2. A compliant GraphQL Server - With URQL setup none of the operations were being validated. I found a lot of inconsistencies within the GraphQL schema which should be caught early on.

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This is first attempt to improve DX and make contributions easier. There is a lot more we can clean and improve but this already a large PR so should scope more time for follow-ups.