DRAFT: Scan API change to serve create event blobs for RewardCouponV2

Motivation for the API

Enable sophisticated app providers to run delegation-based minting automation by

1. reading the DSO events stream from /v0/events and computing the right splits (likely on a per-tx basis)
2. requesting the required create events blobs
3. submitting commands against their participant node with these disclosed contracts

Getting the blobs is only supported for RewardCouponV2 contracts, as with TBAR the ability to do per-tx reward sharing is gone; and has to be implemented in the form above.

Pull Request Checklist

Cluster Testing

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• If a logical synchronizer upgrade test is required (from canton-3.5), comment /lsu_test on this PR to request it, and ping someone with access to the DA-internal system to approve it.

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