Create a unified GraphQL API using Schema stitching

[makoto]

The problem

When a domain points to L2 gateway resolver, the l1 subgraph can no longer index event information such as text/coin type record and subdomains

Potential solution

• Use GraphqQL's schema stitching to amalgamated subgraphs across the different networks.
• If the gateway fetches data from off-chain (non l2/sidechains), define API to fetch data from off-chain and include it in the amalgamated subraph.
• When there are duplicate information across different chains (eg: matoken.eth resolver first points to Polygon, then repoints to Optimism ), then select the latest data based on which chain the canonical name is bridged to (We are planning to create BridgeRegistrar where a domain name on L2 can only be claimed on our canonical Register contract only when the name asset is transferred to the specific bridge.