feat: add gasSponsored flag to bridgeController (#6687)

## Explanation

### What is the current state of things and why does it need to change?
- Today, quotes can indicate when gas is embedded into the transaction
itself via `gasIncluded` and when EIP‑7702 delegated execution can be
used via `gasIncluded7702`, but there’s no explicit way to signal that a
third party will sponsor the gas cost.
- This prevents the UI/clients from differentiating between “quote
includes gas fees” and “quote is gasless to the user because gas is
sponsored,” which affects UX (badging, prioritization) and any
downstream decision logic.

### What is the solution your changes offer and how does it work?
- Added an optional boolean `quote.gasSponsored` to `QuoteSchema` in
`@validators.ts` to allow the bridge API to flag gas‑sponsored quotes.
- Ensured end‑to‑end preservation:
  - Validation now accepts payloads with or without `gasSponsored`.
- `BridgeController.fetchQuotes` and the fee‑augmentation path preserve
the field unchanged so the UI and metrics layers can consume it.
- Tests:
- Added a test in `bridge-controller.test.ts` verifying that
`fetchQuotes` returns quotes where `quote.gasSponsored` is preserved
when present, and remains undefined when omitted.
- Backward compatibility:
- The field is optional; existing payloads and flows continue to work
unchanged.
  - No sorting or fee calculations are altered by this addition.

### Are there any changes whose purpose might not obvious to those
unfamiliar with the domain?
- Distinction between flags:
- `gasIncluded`: Quote includes gas fees in the trade economics, but the
user still submits and pays gas.
  - `gasIncluded7702`: Quote can use delegated execution under EIP‑7702.
- `gasSponsored`: A third party sponsors the gas so the user doesn’t pay
it; this is orthogonal to whether gas is “included” in pricing or
delegated via 7702.


## References

This PR is related to this BridgeAPI PR
consensys-vertical-apps/va-mmcx-bridge-api#527.
PR related for MM Extension:
MetaMask/metamask-extension#36227.
PR related for MM Mobile:
MetaMask/metamask-mobile#20878.


## Checklist

- [X] I've updated the test suite for new or updated code as appropriate
- [ ] 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]
> Adds optional `quote.gasSponsored` to validation schema and ensures
`fetchQuotes` returns it unchanged; updates tests and changelog.
> 
> - **Validation**:
> - Add optional `quote.gasSponsored` to `QuoteSchema` in
`utils/validators.ts`.
> - **Controller Tests**:
> - Add test verifying `fetchQuotes` preserves `quote.gasSponsored` when
present.
>   - Introduce `makeQuoteRequest` helper for test requests.
> - **Changelog**:
>   - Document new `gasSponsored` property in `fetchQuotes` results.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
c9872a7. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Elliot Winkler <elliot.winkler@gmail.com>

Author: Battambang

packages/bridge-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Quotes as returned by `fetchQuotes` now include a `gasSponsored` property ([#6687](https://github.com/MetaMask/core/pull/6687))
+
 ## [58.0.0]
 
 ### Changed

packages/bridge-controller/src/bridge-controller.test.ts

@@ -26,6 +26,7 @@ import {
   StatusTypes,
   type BridgeControllerMessenger,
   type QuoteResponse,
+  type GenericQuoteRequest,
 } from './types';
 import * as balanceUtils from './utils/balance';
 import { getNativeAssetForChainId, isSolanaChainId } from './utils/bridge';
@@ -2615,6 +2616,21 @@ describe('BridgeController', function () {
     const quotesByDecreasingProcessingTime = [...mockBridgeQuotesSolErc20];
     quotesByDecreasingProcessingTime.reverse();
 
+    const makeQuoteRequest = (
+      overrides: Partial<GenericQuoteRequest> = {},
+    ): GenericQuoteRequest => ({
+      walletAddress: '0x123',
+      srcChainId: 1,
+      destChainId: 10,
+      srcTokenAddress: '0x0000000000000000000000000000000000000000',
+      destTokenAddress: '0x0000000000000000000000000000000000000000',
+      srcTokenAmount: '1000',
+      slippage: 0.5,
+      gasIncluded: false,
+      gasIncluded7702: false,
+      ...overrides,
+    });
+
     beforeEach(() => {
       jest.clearAllMocks();
       jest
@@ -2845,6 +2861,33 @@ describe('BridgeController', function () {
       expect(quotes).toStrictEqual(mockBridgeQuotesSolErc20);
       expect(bridgeController.state).toStrictEqual(expectedControllerState);
     });
+
+    it('should preserve gasSponsored flag on quotes', async () => {
+      const firstQuoteWithFlag: QuoteResponse = {
+        ...mockBridgeQuotesNativeErc20Eth[0],
+        quote: {
+          ...mockBridgeQuotesNativeErc20Eth[0].quote,
+          gasSponsored: true,
+        },
+      } as QuoteResponse;
+      const secondQuote: QuoteResponse =
+        mockBridgeQuotesNativeErc20Eth[1] as QuoteResponse;
+      const quotesWithFlag: QuoteResponse[] = [firstQuoteWithFlag, secondQuote];
+
+      const fetchBridgeQuotesSpy = jest
+        .spyOn(fetchUtils, 'fetchBridgeQuotes')
+        .mockResolvedValueOnce({
+          quotes: quotesWithFlag,
+          validationFailures: [],
+        });
+
+      const quotes = await bridgeController.fetchQuotes(makeQuoteRequest());
+
+      expect(fetchBridgeQuotesSpy).toHaveBeenCalledTimes(1);
+      expect(quotes).toHaveLength(2);
+      expect(quotes[0].quote.gasSponsored).toBe(true);
+      expect(quotes[1].quote.gasSponsored).toBeUndefined();
+    });
   });
 
   describe('metadata', () => {

packages/bridge-controller/src/utils/validators.ts

@@ -244,6 +244,10 @@ export const QuoteSchema = type({
       totalFeeAmountUsd: optional(string()),
     }),
   ),
+  /**
+   * A third party sponsors the gas. If true, then gasIncluded7702 is also true.
+   */
+  gasSponsored: optional(boolean()),
 });
 
 export const TxDataSchema = type({