fix: handle zero disbursed amount for check_disbursal function (#1229)

lana/app/src/credit_facility/entity.rs

@@ -254,7 +254,13 @@ impl FacilityCVL {
     }
 
     fn check_disbursal_allowed(&self, terms: TermValues) -> Result<(), CreditFacilityError> {
-        if self.disbursed < terms.margin_call_cvl {
+        let cvl = if self.disbursed.is_zero() {
+            self.total
+        } else {
+            self.disbursed
+        };
+
+        if cvl < terms.margin_call_cvl {
             return Err(CreditFacilityError::BelowMarginLimit);
         }
         Ok(())
@@ -1745,6 +1751,20 @@ mod test {
         ));
     }
 
+    #[test]
+    fn cvl_check_disbursal_allowed_for_zero_amount() {
+        let terms = default_terms();
+
+        let facility_cvl = FacilityCVL {
+            total: terms.margin_call_cvl,
+            disbursed: CVLPct::ZERO,
+        };
+        assert!(matches!(
+            facility_cvl.check_disbursal_allowed(terms),
+            Ok(())
+        ));
+    }
+
     #[test]
     fn check_activated_at() {
         let mut credit_facility = facility_from(initial_events());

lana/app/src/terms/value.rs

@@ -131,6 +131,10 @@ impl CVLPct {
         Self(Decimal::from(value))
     }
 
+    pub fn is_zero(&self) -> bool {
+        *self == Self::ZERO
+    }
+
     pub fn scale(&self, value: UsdCents) -> UsdCents {
         let cents = value.to_usd() * dec!(100) * (self.0 / dec!(100));
         UsdCents::from(