add: add cash transaction fodler model and crud for this model

core/apps/finance/serializers/cash_transaction.py

@@ -6,6 +6,7 @@ from core.apps.finance.models import CashTransaction
 from core.apps.accounts.models import User
 from core.apps.finance.models import PaymentType
 
+
 class CashTransactionEmployeeListSerializer(serializers.ModelSerializer):
     class Meta:
         model = User 

core/apps/finance/serializers/cash_transaction_folder.py

@@ -0,0 +1,20 @@
+from rest_framework import serializers
+
+from core.apps.finance.models import CashTransactionFolder
+
+
+class CashTransactionFolderSerializer(serializers.ModelSerializer):
+    cash_transaction_count = serializers.SerializerMethodField(method_name='get_cash_transaction_count')
+
+    class Meta:
+        model = CashTransactionFolder
+        fields = [
+            'id', 'name', 'cash_transaction_count'
+        ]
+        extra_kwargs = {
+            'id': {"read_only": True},
+            'cash_transaction_count': {"read_only": True},
+        }
+
+    def get_cash_transaction_count(self, obj):
+        return obj.cash_transactions.count()