Add a scanning results reader

[upbqdn]

Motivation

So far, we have only used ldb to print the contents of the storage with the scanning results. Since the results contain only TXIDs, we couldn't straightforwardly tell much about their properties.

Depends-On: #8079.

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Solution

• Add a separate binary into zebra-utils that prints Zebra's scanning results:

  1. Open Zebra's scanning storage and read the results containing scanning keys and TXIDs.
  2. Fetch the transactions by their TXIDs from Zebra using the getrawtransaction RPC.
  3. Decrypt the TX outputs using the corresponding scanning key.
  4. Print the memos in the outputs.

• Add a tutorial describing how to use the tool.

Testing

I didn't add or change any tests.

Review

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[teor2345]

Looks great!

I wonder if we could move some of this code into scan.rs, or maybe a separate decrypt.rs module? I could imagine two APIs:

• high-level: key string, transaction data bytes, Zebra network, height, returns Zebra typed memo data
• low-level: zcash_primitives key type, transaction type, network, heights, returns raw or zcash_primitives memo data

This could happen in a separate ticket.

[teor2345]

Happy to merge this now and do any other changes in another PR. Or do the changes here. Totally up to you!

[upbqdn]

I'd prefer to make the changes here. I should be done by tomorrow.

[teor2345]

Let's go! Then we can do some cleanups later.