support creating decimal from u128 type

Author: 0xripleys

contracts/suilend/sources/decimal.move

@@ -14,6 +14,12 @@ module suilend::decimal {
         }
     }
 
+    public fun from_u128(v: u128): Decimal {
+        Decimal {
+            value: (v as u256) * WAD
+        }
+    }
+
     public fun from_percent(v: u8): Decimal {
         Decimal {
             value: (v as u256) * WAD / 100,
@@ -159,7 +165,8 @@ module suilend::decimal_tests {
         from,
         from_percent,
         saturating_sub,
-        saturating_floor
+        saturating_floor,
+        from_u128
     };
 
     #[test]
@@ -180,10 +187,8 @@ module suilend::decimal_tests {
         assert!(saturating_sub(a, b) == from(0), 0);
         assert!(saturating_sub(b, a) == from(1), 0);
         assert!(saturating_floor(from(18446744073709551615)) == 18446744073709551615, 0);
-        assert!(
-            saturating_floor(add(from(18446744073709551615), from(1))) == 18446744073709551615,
-            0,
-        );
+        assert!(saturating_floor(add(from(18446744073709551615), from(1))) == 18446744073709551615, 0);
+        assert!(from_u128(340282366920938463463374607431768211455).add(from(1)).to_scaled_val() == 340282366920938463463374607431768211456 * 1000000000000000000, 0);
     }
 
     #[test]