Wire index/add handler to write derived hoverboard block level index

[Gozala]

Context

Hoverboard facilitates reads over bitswap. It receives request for the block and looks up index in the dynamo prod-ep-v1-blocks-cars-position table which maps block multihash to CAR (bucket) paths. From the car path it derives CAR multihash and attempts to reads from preconfigured R2 and S3 buckets.

What

• Derive block level index records from dag index, passed into implement index/add handler #1401, and write them into dynamo table.
• ❗️Note that we should also create a record that spans the whole blob range even if it is not manually described in shards

Why

Otherwise content uploaded through blob/add will not be readable via bitswap

Deliverable

Reading blocks uploaded through blob/add and published via index/add should be readable via bitswap from web3.storage peer.

[Gozala]

❗️Note that we should also create a record that spans the whole blob range even if it is not manually described in shards

I am just realizing that this may not be possible per current spec because size of the blob itself is not captured, we probably should amend spec to fix that

[alanshaw]

resolved in storacha/w3infra#363