Add ext txn hash to update api

[jagathweerasinghe-da]

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[Copilot]

Pull request overview

Adds support for propagating an externally-signed transaction hash through Scan’s update history HTTP API encoding/decoding and API schema, so clients can correlate external submissions with committed transactions.

Changes:

• Extend update-history transaction encodings to include externalTransactionHash (HTTP string ↔ Ledger API ByteString).
• Plumb externalTransactionHash through v1→v2 update conversion in the Scan HTTP handler.
• Update OpenAPI schema and adjust tests to cover the new field.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
apps/scan/src/main/scala/org/lfdecentralizedtrust/splice/scan/admin/http/ScanHttpEncodings.scala	Adds encoding/decoding of externalTransactionHash between Ledger API transactions and HTTP update-history payloads.
apps/scan/src/main/scala/org/lfdecentralizedtrust/splice/scan/admin/http/HttpScanHandler.scala	Ensures the hash is preserved when converting update-history transactions to the v2 representation.
apps/scan/src/main/openapi/scan.yaml	Documents the new external_transaction_hash field on update-history transaction schemas.
apps/scan/src/test/scala/org/lfdecentralizedtrust/splice/scan/admin/http/ScanHttpEncodingsTest.scala	Extends round-trip encoding tests to include an external transaction hash.
apps/common/src/test/scala/org/lfdecentralizedtrust/splice/store/StoreTestBase.scala	Updates test transaction builder to accept an external transaction hash.

Comments suppressed due to low confidence (4)

apps/scan/src/main/scala/org/lfdecentralizedtrust/splice/scan/admin/http/ScanHttpEncodings.scala:47

• hexHashOption hand-rolls ByteString -> hex encoding via string formatting, while decoding uses HexFormat.parseHex. There is already a shared com.digitalasset.canton.util.HexString utility in the codebase for hex encoding/decoding; using it here would keep encoding/decoding symmetric and avoids maintaining custom formatting logic.

  private def hexHashOption(extTxnHash: ByteString): Option[String] = {
    if (extTxnHash.isEmpty) {
      None
    } else {
      Some(extTxnHash.toByteArray.map("%02x" format _).mkString)
    }

apps/scan/src/main/scala/org/lfdecentralizedtrust/splice/scan/admin/http/ScanHttpEncodings.scala:271

• Decoding externalTransactionHash via HexFormat.of().parseHex will throw an IllegalArgumentException on invalid input, which will bubble up without context. Consider using the existing hex parsing utility (e.g., HexString.parseToByteString) and failing with a clearer error message if the string is not valid hex.

            http.externalTransactionHash
              .map(hex => ByteString.copyFrom(HexFormat.of().parseHex(hex)))
              .getOrElse(ByteString.EMPTY),

apps/scan/src/main/openapi/scan.yaml:2388

• Grammar: "For transaction externally signed" is ungrammatical/ambiguous. Consider rewording to something like "For externally signed transactions" (and optionally clarify that the value is a hex-encoded hash).

            For transaction externally signed, contains the external transaction hash
            signed by the external party. Can be used to correlate an external submission with a committed transaction.

apps/scan/src/main/openapi/scan.yaml:2451

• Grammar: "For transaction externally signed" is ungrammatical/ambiguous. Consider rewording to something like "For externally signed transactions" (and optionally clarify that the value is a hex-encoded hash).

            For transaction externally signed, contains the external transaction hash
            signed by the external party. Can be used to correlate an external submission with a committed transaction.