Add missing headers in currentCustomerAccountBalance.h

src/currentCustomerAccountBalance.h

@@ -4,4 +4,7 @@
 #include <stdlib.h>
 
 #define MAX_LENGTH 100
-float getAvailableAccountBalance(int user_id);
+
+float getAvailableAccountBalance(int user_id);
+float fetchBalanceFromBalanceString(char balance_String[MAX_LENGTH]);
+float readFileAndGetAvailableBalance(FILE *file, char stringID[MAX_LENGTH]);