* Add subgraph schema types to the generated schema
* Add queries for subgraph entities
* Add entity generation for subgraph entities
* Call subgraph event handler in indexer
* Refactor subgraph schema and entity generation
* Add resolvers generation for subgraph entities
* Get event signature in the event
* Add NonNullType check for field type in entity generation
* Auto-diff based on store set
* Use contract address from data source in loader
* Change subgraph-schema arg to subgraph-path arg