feat(b4w): add human-readable B4wExport repr/str output; fix comdirect account lookup and export formatting helpers

tests/test_model_b4wexport.py

@@ -1,3 +1,5 @@
+import re
+
 import pytest
 from pydantic import ValidationError
 
@@ -29,3 +31,22 @@ def test_b4w_export_account_iban_to_long():
 def test_b4w_export_account_iban_to_short():
     with pytest.raises(ValidationError):
         _ = B4wExportFactory.build(OwnrAcctIBAN="DE123")
+
+
+def test_b4w_export_parameters_to_str():
+    data = B4wExportFactory.build()
+    params = data.parameters_to_str()
+    components = [s.strip() for s in re.split(r",\s*(?=\w+=)", params)]
+    param_names = [component.split("=")[0].strip() for component in components]
+    param_values = [component.split("=")[1].strip() for component in components]
+    assert "OwnrAcctCcy" in param_names
+    assert all(s.startswith("'") and s.endswith("'") for s in param_values)
+
+
+def test_b4w_export_repr_round_trip():
+    data_batch = B4wExportFactory.batch(size=10)
+    assert isinstance(data_batch, list)
+    for data in data_batch:
+        data_str = str(data)
+        data2 = eval(data_str)
+        assert data == data2