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_entry/processor_test.rb

@@ -83,17 +83,89 @@ class EnableBankingEntry::ProcessorTest < ActiveSupport::TestCase
     end
   end
 
-  test "raises ArgumentError when both transaction_id and entry_reference are nil" do
+  # --- compute_external_id unit tests ---
+
+  test "compute_external_id returns transaction_id-based id when present" do
+    assert_equal "enable_banking_txn_abc",
+      EnableBankingEntry::Processor.compute_external_id(transaction_id: "txn_abc", entry_reference: "ref_xyz")
+  end
+
+  test "compute_external_id falls back to entry_reference when transaction_id is blank" do
+    assert_equal "enable_banking_ref_xyz",
+      EnableBankingEntry::Processor.compute_external_id(transaction_id: nil, entry_reference: "ref_xyz")
+  end
+
+  test "compute_external_id returns content fingerprint when both id fields are absent" do
+    tx = {
+      booking_date: "2026-03-15",
+      transaction_amount: { amount: "42.00", currency: "EUR" },
+      credit_debit_indicator: "DBIT",
+      creditor: { name: "Spar" }
+    }
+    result = EnableBankingEntry::Processor.compute_external_id(tx)
+    assert result.start_with?("enable_banking_content_"), "Expected content fingerprint, got: #{result}"
+  end
+
+  test "compute_external_id fingerprint is stable across calls" do
+    tx = {
+      booking_date: "2026-03-15",
+      transaction_amount: { amount: "42.00", currency: "EUR" },
+      credit_debit_indicator: "DBIT",
+      creditor: { name: "Spar" }
+    }
+    assert_equal EnableBankingEntry::Processor.compute_external_id(tx),
+                 EnableBankingEntry::Processor.compute_external_id(tx)
+  end
+
+  test "compute_external_id returns nil for transaction with no identifiable content" do
+    assert_nil EnableBankingEntry::Processor.compute_external_id({})
+    assert_nil EnableBankingEntry::Processor.compute_external_id(transaction_id: nil, entry_reference: nil)
+  end
+
+  # --- ID-less transaction processing ---
+
+  test "imports transaction using content fingerprint when transaction_id and entry_reference are absent" do
     tx = {
       transaction_id: nil,
       entry_reference: nil,
       booking_date: Date.current.to_s,
       transaction_amount: { amount: "10.00", currency: "EUR" },
-      creditor: { name: "Test" },
+      creditor: { name: "Lidl" },
       credit_debit_indicator: "DBIT",
       status: "BOOK"
     }
 
+    assert_difference "@account.entries.count", 1 do
+      EnableBankingEntry::Processor.new(tx, enable_banking_account: @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 "does not create duplicate when same id-less transaction is processed twice" do
+    tx = {
+      transaction_id: nil,
+      entry_reference: nil,
+      booking_date: Date.current.to_s,
+      transaction_amount: { amount: "10.00", currency: "EUR" },
+      creditor: { name: "Lidl" },
+      credit_debit_indicator: "DBIT",
+      status: "BOOK"
+    }
+
+    assert_difference "@account.entries.count", 1 do
+      EnableBankingEntry::Processor.new(tx, enable_banking_account: @enable_banking_account).process
+    end
+
+    assert_no_difference "@account.entries.count" do
+      EnableBankingEntry::Processor.new(tx, enable_banking_account: @enable_banking_account).process
+    end
+  end
+
+  test "raises ArgumentError for transaction with no identifiable content at all" do
+    tx = { transaction_id: nil, entry_reference: nil }
+
     assert_raises(ArgumentError) do
       EnableBankingEntry::Processor.new(tx, enable_banking_account: @enable_banking_account).process
     end