fix(enable-banking): import transactions missing transaction_id and entry_reference (#1767)

* fix(enable-banking): handle transactions missing transaction_id and entry_reference

Some ASPSPs omit both transaction_id and entry_reference from their transaction payloads, which is valid per the PSD2/Berlin Group spec. Previously, every such transaction raised an ArgumentError and was silently dropped during sync.

compute_external_id now falls back to a deterministic MD5 fingerprint (prefixed enable_banking_content_) derived from date, amount, currency, direction, counterparty, and remittance info. This fingerprint is stable across re-syncs, so duplicate imports are still correctly prevented. An ArgumentError is only raised for truly empty/unidentifiable payloads.

The importer is updated in three places to use compute_external_id
consistently: the pending pre-filter (before combining with booked),
the C4 stored-pending cleanup, and the new_transactions dedup. This means ID-less pending entries are now also removed when their settled booked counterpart arrives.

Tests cover compute_external_id directly (all 5 cases), end-to-end
fingerprint import, idempotency, and importer storage/dedup behaviour for ID-less transactions including the pending→booked settlement path.

* fix(enable-banking): implement dual-strategy matching for transaction settlement

When a stored pending row had only entry_reference (no transaction_id) and
the settled BOOK row arrived with a new transaction_id, compute_external_id
produced different fingerprints for each side (enable_banking_<ref> vs
enable_banking_<txn_id>). The fingerprint-only comparison introduced in the
previous commit never matched, leaving the stale pending entry in
raw_transactions_payload. Both rows were then imported as separate visible
transactions.

Restore a book_entry_refs set alongside book_fingerprints in both the
pending pre-filter and the C4 stored-pending cleanup. A pending entry is
now removed when either its fingerprint or its entry_reference matches a
booked counterpart — covering same-ID settlement, content-fingerprint
settlement, and the entry_reference cross-match settlement path.

Also updates the ArgumentError message in external_id to accurately
reflect that transaction_id, entry_reference, and content fingerprint
are all accepted identifiers, and aligns build_transaction_content_key
to use transaction_date as a fallback (matching compute_external_id).

Adds a regression test that stores a pending-only row and asserts it is removed when the booked counterpart arrives with a new transaction_id.

test/models/enable_banking_account/transactions/processor_test.rb

@@ -157,6 +157,38 @@ class EnableBankingAccount::Transactions::ProcessorTest < ActiveSupport::TestCas
     assert_equal 1, result[:imported]
   end
 
+  test "imports id-less transaction using content fingerprint" do
+    tx = {
+      "booking_date" => Date.current.to_s,
+      "transaction_amount" => { "amount" => "19.99", "currency" => "EUR" },
+      "credit_debit_indicator" => "DBIT",
+      "creditor" => { "name" => "Spotify" }
+    }
+    @enable_banking_account.update!(raw_transactions_payload: [ tx ])
+
+    assert_difference "@account.entries.count", 1 do
+      EnableBankingAccount::Transactions::Processor.new(@enable_banking_account).process
+    end
+
+    expected_id = EnableBankingEntry::Processor.compute_external_id(tx)
+    assert @account.entries.exists?(external_id: expected_id, source: "enable_banking")
+  end
+
+  test "id-less transaction does not appear in failed count" do
+    tx = {
+      "booking_date" => Date.current.to_s,
+      "transaction_amount" => { "amount" => "5.00", "currency" => "EUR" },
+      "credit_debit_indicator" => "CRDT",
+      "debtor" => { "name" => "Employer" }
+    }
+    @enable_banking_account.update!(raw_transactions_payload: [ tx ])
+
+    result = EnableBankingAccount::Transactions::Processor.new(@enable_banking_account).process
+
+    assert_equal 0, result[:failed]
+    assert_equal 1, result[:imported]
+  end
+
   test "handles empty raw_transactions_payload gracefully" do
     @enable_banking_account.update!(raw_transactions_payload: nil)