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
@@ -144,7 +150,7 @@ module suilend::decimal {
 
 #[test_only]
 module suilend::decimal_tests {
-    use suilend::decimal::{add, sub, mul, div, floor, ceil, pow, lt, gt, le, ge, from, from_percent, saturating_sub, saturating_floor};
+    use suilend::decimal::{add, sub, mul, div, floor, ceil, pow, lt, gt, le, ge, from, from_percent, saturating_sub, saturating_floor, from_u128};
 
     #[test]
     fun test_basic() {
@@ -165,6 +171,7 @@ module suilend::decimal_tests {
         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!(from_u128(340282366920938463463374607431768211455).add(from(1)).to_scaled_val() == 340282366920938463463374607431768211456 * 1000000000000000000, 0);
     }
 
     #[test]