add contract models and register this models admin panel

core/apps/contracts/enums/contract_notification.py

@@ -0,0 +1,15 @@
+NOTIFICATION_EVENT = (
+    ('exact_date', 'exact date'),
+    ('counterparty_signing', 'counterparty signing'),
+    ('signature_all_parties', 'Signature of all parties')
+)
+
+TYPE_NOTIFICATION = (
+    ('sms', 'sms'),
+    ('whatsup', 'whatsup'),
+)
+
+TYPE_MESSAGE = (
+    ('krill', 'krill'),
+    ('latin', 'latin'),
+)