Feature request: assertion helper for "a tapped request had a JSON body like..."

[jwadhams]

Context

A recurring pattern in consumer test suites (found while reviewing services/incentives's LexusIncentivesServiceTest) is: find the one GuzzleTapper-captured request matching a method+URL, decode its JSON body, and assert on specific fields — to prove the actual outbound request carried the right data, not just that a mocked response was returned correctly.

Current code to do this (4 lines, every time):

$offersCall = $tapper->getCalls()
    ->first(fn ($request) => str_contains((string) $request->getUri(), 'inventoryservices.lexusdealerdigital.com'));
$this->assertNotNull($offersCall, 'Expected a call to the Lexus offers API.');
$sentBody = json_decode((string) $offersCall->getBody(), true);
$this->assertSame('08052', $sentBody['zip'], 'Zip sent to Lexus must come from Customer API, not the request.');

Proposal

Add a helper to Carsdotcom\ApiRequest\Testing\RequestClassAssertions (the existing trait that already holds assertRequestCacheBodyContains), something like:

protected static function assertTapperSentJsonBodyLike(
    GuzzleTapper $tapper,
    string $method,
    string $urlPattern,
    array $expectedBodySubset,
    string $message = '',
): void

• Reuses GuzzleTapper::getCalls() and the same preg_match($urlPattern, ...) matching convention GuzzleTapper::getCountLike() already uses, so behavior stays consistent with the rest of the class.
• Fails clearly if no request matched method+urlPattern at all (distinct from "matched, but body was wrong").
• Asserts $expectedBodySubset as a subset of the decoded JSON body (like assertArraySubset/Laravel's assertJson), not an exact match — so a caller only pins down the field(s) they actually care about.

Collapses the 4-line pattern above to:

$this->assertTapperSentJsonBodyLike(
    $tapper,
    'POST',
    '#inventoryservices\.lexusdealerdigital\.com#',
    ['zip' => '08052'],
    'Zip sent to Lexus must come from Customer API, not the request.',
);

Happy to put up a PR with this if the shape looks right — mostly wanted to check the API design before writing it, since it needs to fit alongside GuzzleTapper's existing getCountLike()/getCount() conventions.