[add]: loan charges and offers. Fix RACCheck

app/models/loan.py

@@ -48,8 +48,8 @@ class Loan(db.Model):
     def create_loan(cls, customer_id, account_id, offer_id, product_id, initial_loan_amount, collection_type, transaction_id, status='pending'):
 
         # Check if customer exists
-        is_valid = Customer.is_valid_customer(customer_id)
-        if not is_valid:
+        customer = Customer.is_valid_customer(customer_id)
+        if not customer:
             raise ValueError("Customer does not exist")
 
         now = datetime.now(timezone.utc)
@@ -67,7 +67,7 @@ class Loan(db.Model):
             due_date=now, 
             status = status
         )
-
+        
         try:
             db.session.add(loan)
         except IntegrityError as err: