Add /event/party field with agent and customer values

Add new /event/party enum field to specify which party is submitting the
transaction. Valid values are "agent" and "customer". The field is
positioned first in the event object.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: horgh

HISTORY.rst

@@ -11,6 +11,8 @@ History
 * Added ``securepay`` to the ``/payment/processor`` validation.
 * Added ``credit_application`` and ``fund_transfer`` to the ``/event/type``
   validation.
+* Added the input ``/event/party``. This is the party submitting the
+  transaction.
 
 3.1.0 (2025-05-23)
 ++++++++++++++++++

README.rst

@@ -156,6 +156,7 @@ Score, Insights and Factors Example
     >>>         'user_agent': 'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.89 Safari/537.36'
     >>>     },
     >>>     'event': {
+    >>>         'party': 'customer',
     >>>         'shop_id': 's2123',
     >>>         'type': 'purchase',
     >>>         'transaction_id': 'txn3134133',

src/minfraud/validation.py

@@ -281,6 +281,8 @@ def _credit_card_token(s: str) -> str:
 )
 
 
+_event_party = In(["agent", "customer"])
+
 _event_type = In(
     [
         "account_creation",
@@ -348,6 +350,7 @@ def _uri(s: str) -> str:
             "domain": _hostname,
         },
         "event": {
+            "party": _event_party,
             "shop_id": str,
             "time": _rfc3339_datetime,
             "type": _event_type,

tests/data/full-transaction-request.json

@@ -1,5 +1,6 @@
 {
   "event": {
+    "party": "customer",
     "transaction_id": "txn3134133",
     "shop_id": "s2123",
     "time": "2014-04-12T23:20:50.052+00:00",

tests/test_validation.py

@@ -308,6 +308,12 @@ def test_domain(self) -> None:
 
 
 class TestEvent(ValidationBase, unittest.TestCase):
+    def test_party(self) -> None:
+        for good in ("agent", "customer"):
+            self.check_transaction({"event": {"party": good}})
+        for bad in ("bad", 1, ""):
+            self.check_invalid_transaction({"event": {"party": bad}})
+
     def test_transaction(self) -> None:
         self.check_transaction_str_type("event", "transaction_id")