feat(api): add 22 missing Transaction variants and Unknown catchall -- fixes #41

[leftygbalogh]

feat(api): add 22 missing Transaction variants and Unknown catchall

Problem

The Transaction enum in xrpl_api uses #[serde(tag = "TransactionType")] for deserialization. 22 XRPL protocol-level transaction types were missing from the enum. When any of these types appears in an inbound payload, Serde returns a hard Err("unknown variant \"…\""), with no recovery path.

In practice this means:

• WebSocket subscription streams break — a single unrecognised Transaction in the stream aborts the entire TransactionEvent pipeline (the path issue Query Around TransactionType Support #41 reporter hit).
• account_tx batch responses abort — a single unrecognised type in the Vec<AccountTransaction> fails the whole deserialization. A commented-out // pub tx: serde_json::Value in account_tx.rs shows a previous developer already hit this.
• Any code embedding Transaction (e.g., TxResponse, AccountTxResponse) is affected.

Fixes #41. Related: #39.

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Solution

1. 22 missing variants added

Each missing variant is added as VariantName(TransactionCommon). This preserves deserialization of all common fields (Account, Fee, Sequence, flags, memos, signers, etc.) while silently dropping variant-specific fields.

BASELINE contract — intentional lossy deserialization:
Variant-specific fields (e.g., Amount on AMMCreate, PriceDataSeries on OracleSet, XChainBridge on XChainCreateBridge) are not modelled and are silently dropped by Serde on deserialization. Each new variant carries a // BASELINE: variant-specific fields are not modelled and are silently dropped comment to make this explicit. Callers requiring variant-specific data should deserialize to serde_json::Value until those fields are modelled in follow-up PRs.

Variants added by amendment family (audited against xrpl.org/amendments.html, 2026-04-05):

Family	Variants
AMM	AMMBid, AMMCreate, AMMDelete, AMMDeposit, AMMVote, AMMWithdraw
Clawback	Clawback
DID	DIDDelete, DIDSet
Oracle	OracleDelete, OracleSet
Pseudo-transactions	EnableAmendment, SetFee, UNLModify
XChain	XChainAccountCreateCommit, XChainAddAccountCreateAttestation, XChainAddClaimAttestation, XChainClaim, XChainCommit, XChainCreateBridge, XChainCreateClaimID, XChainModifyBridge

2. #[serde(other)] Unknown forward-compatibility catchall

A Unknown unit variant is added with #[serde(other)]. Any TransactionType string not present in the enum — including future amendment-gated types — deserializes to Unknown rather than returning Err. This prevents stream and batch aborts on types that postdate this PR.

Unknown contract:
Unknown is a unit variant (carries no inner data — a constraint of #[serde(other)] with an internally-tagged enum). transaction.common() and transaction.common_mut() are unreachable on Unknown and will panic with unreachable!() if called. Callers should match on Transaction::Unknown before calling common() when handling events from unknown transaction types.

3. common() / common_mut() updated

All 22 new named variants are handled identically to existing TransactionCommon-wrapping variants. Unknown arms use unreachable!().

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Test coverage

50 tests pass, 0 failing, across the full workspace.

Test	What it proves
22 × test_deserialize_<VariantName>	One round-trip per new variant — common fields survive
test_deserialize_unknown_variant_does_not_panic	Unknown catchall — unrecognised TransactionType no longer returns Err
test_deserialize_existing_variants_still_work	Regression guard — pre-existing variants unaffected
test_account_tx_response_fails_on_unknown_transaction_type	AccountTxResponse batch embedding path
test_tx_response_fails_on_unknown_transaction_type	TxResponse single-lookup embedding path
test_transaction_event_fails_on_unknown_transaction_type	TransactionEvent / WebSocket stream path
test_amm_create_real_payload_common_fields_correct_variant_fields_dropped	AMMCreate real-world JSON — flat fields (Amount, Amount2, TradingFee) silently dropped
test_oracle_set_real_payload_nested_array_silently_dropped	OracleSet real-world JSON — nested PriceDataSeries array silently dropped
test_x_chain_create_bridge_real_payload_nested_object_silently_dropped	XChainCreateBridge real-world JSON — nested XChainBridge object silently dropped
test_amm_deposit_real_payload_multi_field_silently_dropped	AMMDeposit real-world JSON — multi-field mix silently dropped

Fixture JSON payloads are sourced from official XRPL documentation examples (xrpl.org) and verify the BASELINE lossy contract under realistic conditions.

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CI

cargo test             # full workspace: 50/50 passing
cargo clippy -p xrpl_api  # 0 warnings
cargo fmt --check      # files modified by this PR are clean

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Out of scope / follow-up

• Variant-specific field modelling — recommended as a separate PR per amendment family.
• Option<&TransactionCommon> return type on common() / common_mut() — deferred; would be a breaking public API change; warrants its own discussion.