ADR-040 Implementation: Migrate storage command/script for store v2

[roysc]

Summary

We need to provide a command for users to migrate data from the existing IAVL-based state to the new SMT-based store/v2.

Problem Definition

ADR-040 introduces a new state storage format using SMT as the commitment scheme, with a new internal storage format. In order to use it with an existing app, data will have to be migrated from the v1 store/MultiStore. This will need to happen at a predetermined block height like all StoreUpgrades.

Data can be dumped and read back as JSON. From discussions in vulcanize#7, this should not require new tooling, but it probably cannot be done internally and automatically by modules. Assuming it cannot, we need to create a script and command to ensure it is done gracefully, and is convenient and well documented for SDK users.

Steps:

• iterate over all store keys and save them (without Cache layer) to store/v2
• send an IBC UpgradeClient request with the new client state

Proposal

• Implement an app command which is to be manually run on an offline chain.
• Upon next running the chain, the UpgradeClient event is emitted.
• The original database contents are not deleted or modified until the migration successfully completes.
  • Deletion could be left to an additional manual command.
• TODO: additional steps or considerations?

(TODO)

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For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned

[roysc]

@robert-zaremba could you add any existing notes/thoughts to the description?

[robert-zaremba]

I think this is not needed: let's chat about it today. Migration will be "on fly" or through genesis export-import

[robert-zaremba]

So instead of a user stopping an app and calling the store migration command, this will be handled in on fly migration #10891.