fix(graphql): serialize USDT fee probe amounts

src/graphql/shared/types/scalar/usd-cents.ts

@@ -1,4 +1,4 @@
-import { USDAmount } from "@domain/shared"
+import { USDAmount, USDTAmount } from "@domain/shared"
 import { GT } from "@graphql/index"
 
 const USDCentsScalar = GT.Scalar({
@@ -16,6 +16,9 @@ const USDCentsScalar = GT.Scalar({
         if (value instanceof USDAmount) {
             return Number(value.asCents(2)) 
         }
+        if (value instanceof USDTAmount) {
+            return Number(value.asSmallestUnits())
+        }
         else throw new Error(`Failed to serialize USDAmount: ${value}`)
     }
 })

test/flash/unit/graphql/shared/types/scalar/usd-cents.spec.ts

@@ -0,0 +1,18 @@
+import { USDAmount, USDTAmount } from "@domain/shared"
+import USDCentsScalar from "@graphql/shared/types/scalar/usd-cents"
+
+describe("USDCentsScalar", () => {
+  it("serializes USD amounts as cents", () => {
+    const amount = USDAmount.cents("123")
+    if (amount instanceof Error) throw amount
+
+    expect(USDCentsScalar.serialize(amount)).toBe(123)
+  })
+
+  it("serializes USDT amounts as micro-USDT units", () => {
+    const amount = USDTAmount.smallestUnits("1234567")
+    if (amount instanceof Error) throw amount
+
+    expect(USDCentsScalar.serialize(amount)).toBe(1234567)
+  })
+})