fix: strip multi-digit array indices from query string

[JasonHolderness-bl]

Problem

QueryStringCleanerMiddleware::buildQuery() and LeverClient::prepareOptions() both use:

preg_replace('/%5B[0-9]%5D/', '', $query)

That pattern matches %5B + exactly one digit + %5D, so it strips %5B0%5D through %5B9%5D but leaves %5B10%5D, %5B11%5D, ... intact.

When a caller chains the same builder method more than 10 times, e.g.:

$client = $lever->opportunities()->performAs($userId);
foreach ($postingIds as $id) {           // 12 posting IDs
    $client->posting($id);
}
$client->fetch();

http_build_query() indexes the array, the regex strips the first ten, and the final URL is a mix of clean and array-indexed parameters:

opportunities
  ?posting_id=...&posting_id=...&...&posting_id=...   ← first 10 cleaned
  &posting_id%5B10%5D=...&posting_id%5B11%5D=...      ← left behind

Lever's API rejects these requests, causing downstream production errors.

Fix

Switch both regexes to /%5B\d+%5D/ so any numeric index is stripped regardless of digit count. Behavior for batches ≤10 is unchanged.

Test

Added OpportunitiesTest::retrieve_opportunities_with_more_than_ten_postings_strips_all_array_indices, which calls ->posting() 12 times and asserts:

• No %5B (URL-encoded [) anywhere in the URL
• posting_id[ (decoded form) does not appear
• Exactly 12 posting_id= parameters
• Each provided UUID is present

I verified the new test fails against the old single-digit regex and passes with the multi-digit fix. Existing test suite (17 tests, 56 assertions) remains green.

Downstream context

Found while debugging Bugsnag errors in a Laravel app that batches up to ~30 posting_id parameters in a single opportunities request. The application now bypasses the fluent builder as a workaround; once this fix is released we can drop the workaround.