Research possible support for indexer/admin GraphQL endpoints

[dotansimha]

This architecture is really awesome. if we could have a health-check endpoint to get chainHeadBlock, its also helpful. I think the following is an ideal configuration.

Current configuration ==>

sources:

• name: uniswap_kovan handler: graphql: endpoint: https://api.thegraph.com/subgraphs/name/uniswap/uniswap-kovan

Proposed configuration ==>

sources:

• name: uniswap_kovan handler: graphql: queryEndpoint: https://api.thegraph.com/subgraphs/name/uniswap/uniswap-kovan healthEndpoint: https://api.thegraph.com/index-node/graphql

Originally posted by @wanglonghong in https://github.com/graphprotocol/graph-client/issues/46#issuecomment-1108273307

[dotansimha]

More info on the admin/indexer endpoints and their supported features: https://thegraph.com/docs/en/indexing/#graph-node (the schema is in https://github.com/graphprotocol/graph-node/blob/master/server/index-node/src/schema.graphql )