Migrate Explorer to the Indexer for Explorer

[frol]

Story

Indexer for Explorer is a new syncing backend (#236), which syncs the raw network data reliably and consistently. It also stores all the receipts (intermediate transactions) and execution results, which addresses a ton of issues with the current syncing infrastructure (#212, #218, #223, #352, #358, #404).

Migration Plan

I expect we can run a single Explorer backend capable of serving data from both SQLite (old sync keeps working) and Postgres (filled in by Indexer for Explorer). It seems to be mostly the case already (select-postgres endpoint). Thus, the changes we need to land are only going to be on the frontend side.

• 1. Configure the backend to use Indexer for Explorer database (we also need to add more configuration into backend/config/database.js through environment variables like NEAR_INDEXER_DATABASE_HOST, NEAR_INDEXER_DATABASE_NAME, NEAR_INDEXER_DATABASE_USERNAME, NEAR_INDEXER_DATABASE_PASSWORD), ask @khorolets for credentials.

• 2. Migrate frontend/src/libraries/explorer-wamp/* from select to select:INDEXER_BACKEND

• 3. Make sure that we are feature-complete (all the pages except Nodes Dashboard should be served through Indexer for Explorer; Nodes Dashboard is going to live on SQLite, and it is going to be a separate effort to redesign Telemetry storage if necessary)

• 4. Deploy the new Explorer only for testnet (we may even consider deploying it on a separate domain, e.g. beta.explorer.testnet.near.org), and keep the rest networks as is

• 5. Come up with the solution for GuildNet Explorer (it is a 100%-community-driven network, so we should ask them to run Indexer for Explorer nodes)

• 6. Gradually migrate all the networks to Indexer for Explorer (UPD: testnet and mainnet are migrated, but betanet is still not due to a need to have more automation on network hard-resets)

[frol]

@icerove please, create individual issues for the first two steps of the plan (you may choose to split them into as many issues as you see necessary)

[frol]

I close this issue given mainnet and testnet are completely migrated. Other networks will be supported with the legacy backend for now.