Update ENS Subgraph URL

[gskril]

The ENS subgraph URL used in this repo (https://api.thegraph.com/subgraphs/name/ensdomains/ens) will have a global rate limit added on June 12. To avoid this, it is recommended to create your own API key with TheGraph.

It’s free for the first 100k requests/month, and the ENS DAO Ecosystem Working Group is offering potential sponsorships if you go beyond that. Here is a video walking through the setup process (less than 5 mins).

This is due to TheGraph sunsetting its hosted service. The old URL will begin serving requests from an ENS DAO-sponsored API key, so this is not a breaking change for ENS, but it will introduce a more restrictive rate limit.

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Where the hosted subgraph is used in this repo: https://github.com/streamr-dev/core-frontend/blob/master/codegen.ts#L11