Add /v1/:chainId/about/indexing endpoint

[iamacook]

Summary

This adds a new GET /v1/:chainId/about/indexing endpoint for returning the indexer status relative to the current block timestamp:

type Response = {
  lastSync: number // timestamp of oldest block synced by singleton or ERC-20/721 indexers
  synced: boolean // if Transaction Service returns `true` both singletons and ERC-20/721 indexers
}

Changes

• Add expirationTimeInSeconds.indexing configuration
• Add indexing cache key
• Add IndexingStatusSchema with inferred type/builder
• Add ITransactionApi['getIndexingStatus'] method and implementation
• Add `ChainsRepository['getIndexingStatus'] method
• Add GET /v1/:chainId/about/indexing route with entity
• Add appropriate test coverage

[coveralls]

Pull Request Test Coverage Report for Build 10454748393

Details

• 16 of 32 (50.0%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 46.789%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/datasources/cache/cache.router.ts	1	2	50.0%
src/routes/chains/chains.controller.ts	2	3	66.67%
src/routes/chains/entities/indexing-status.entity.ts	4	6	66.67%
src/domain/chains/chains.repository.ts	1	4	25.0%
src/routes/chains/chains.service.ts	3	7	42.86%
src/datasources/transaction-api/transaction-api.service.ts	1	6	16.67%

Totals
Change from base Build 10454727634:	0.02%
Covered Lines:	4580
Relevant Lines:	7907

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💛 - Coveralls

The base branch was changed.