[add]: Update loan status after repayment

app/api/enums/__init__.py

@@ -1 +1,2 @@
-from .transaction_type import TransactionType
+from .transaction_type import TransactionType
+from .loan_status import LoanStatus

app/api/enums/loan_status.py

@@ -0,0 +1,6 @@
+from enum import Enum
+
+class LoanStatus(str, Enum):
+    PENDING = "pending"
+    ACTIVE = "active"
+    REPAID = "repaid"