fix: relay transaction fees (#7098)

## Explanation

Determine Relay provider fees directly from data with no calculation.

## References

Related to
[#6186](MetaMask/MetaMask-planning#6186)

## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [x] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [x] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Read provider fees directly from Relay response
(`fees.relayer.amountUsd`) and update quote normalization, types, and
tests accordingly.
> 
> - **Relay strategy**
> - **Fee source**: Use `fees.relayer.amountUsd` for provider fee in
`normalizeQuote` instead of deriving from `details`.
> - **Types**: Update `RelayQuote` to remove `details.currencyIn` and
replace `fees.gas` with `fees.relayer` in `src/strategy/relay/types.ts`.
> - **Normalization**: Adjust provider fee calculation in
`src/strategy/relay/relay-quotes.ts`.
> - **Tests**
> - Update `relay-quotes.test.ts` mocks and expectations to align with
new `fees.relayer` structure and provider fee calculation.
> - **Changelog**
>   - Add entry: Read Relay provider fees directly from response.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
b91a4ca. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: matthewwalsh0

packages/transaction-pay-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Read Relay provider fees directly from response ([#7098](https://github.com/MetaMask/core/pull/7098))
+
 ## [4.0.0]
 
 ### Added

packages/transaction-pay-controller/src/strategy/relay/relay-quotes.test.ts

@@ -37,9 +37,6 @@ const QUOTE_REQUEST_MOCK: QuoteRequest = {
 
 const QUOTE_MOCK = {
   details: {
-    currencyIn: {
-      amountUsd: '2.34',
-    },
     currencyOut: {
       amountFormatted: '1.0',
       amountUsd: '1.23',
@@ -51,8 +48,8 @@ const QUOTE_MOCK = {
     timeEstimate: 300,
   },
   fees: {
-    gas: {
-      amountUsd: '3.45',
+    relayer: {
+      amountUsd: '1.11',
     },
   },
   steps: [

packages/transaction-pay-controller/src/strategy/relay/relay-quotes.ts

@@ -164,8 +164,7 @@ function normalizeQuote(
   fullRequest: PayStrategyGetQuotesRequest,
 ): TransactionPayQuote<RelayQuote> {
   const { messenger, transaction } = fullRequest;
-  const { details } = quote;
-  const { currencyIn, currencyOut } = details;
+  const { details, fees } = quote;
 
   const { usdToFiatRate } = getFiatRates(messenger, request);
 
@@ -175,7 +174,7 @@ function normalizeQuote(
   );
 
   const provider = getFiatValueFromUsd(
-    new BigNumber(currencyIn.amountUsd).minus(currencyOut.amountUsd),
+    new BigNumber(fees.relayer.amountUsd),
     usdToFiatRate,
   );
 

packages/transaction-pay-controller/src/strategy/relay/types.ts

@@ -2,9 +2,6 @@ import type { Hex } from '@metamask/utils';
 
 export type RelayQuote = {
   details: {
-    currencyIn: {
-      amountUsd: string;
-    };
     currencyOut: {
       amountFormatted: string;
       amountUsd: string;
@@ -16,7 +13,7 @@ export type RelayQuote = {
     timeEstimate: number;
   };
   fees: {
-    gas: {
+    relayer: {
       amountUsd: string;
     };
   };