fix(openapi): document array query parameters with bracket notation

[soyuka]

Q	A
Branch?	4.4
Bug fix?	yes
New feature?	no
Deprecations?	no
Issues	Fixes #8421
License	MIT

An array-typed QueryParameter with no filter attached was documented in a form API Platform cannot parse back.

The filterless branch of OpenApiFactory::collectPaths() never inspected the schema and never passed style/explode, so OpenApi\Model\Parameter defaulted them to form/true for in: query. That serializes as repeated bare keys (ids=1&ids=2), but RequestParser::parseRequestParams() is built on parse_str, where only the ids[]= bracket form yields an array. A client following the document sent the documented URL and the server kept only the last value.

The filter-backed path already solves this: Doctrine\Common\Filter\OpenApiFilterTrait::getOpenApiParameters() emits key[] and honours the existing tri-state castToArray. This applies the same rule to the filterless path, so no new option is introduced.

Only the OpenAPI parameter name gains the [] suffix. The QueryParameter's key is untouched, because extractParameterValues() looks values up by $parameter->getKey() while RequestParser hex-encodes only the segment before [, yielding the bare key.

Two gates keep this off every existing API. The array variant is emitted only when the parameter is in: query and its declared schema is already type: array:

• schema is not type: array: bare name only, always, whatever castToArray says.
• castToArray: false: bare name only.
• castToArray: true: key[] only.
• castToArray unset: both forms.

Header parameters are excluded: there is no bracket-array wire format for headers.

Both gates are pinned by tests, including a scalar-schema query parameter and an array-schema header parameter, each asserted to emit exactly one unchanged parameter.

One reviewer note: when the user supplies their own openapi: parameter and both forms are emitted, their customization is merged into each. Setting castToArray explicitly narrows it to one.

getFilterParameter() and the filter-backed branch are untouched.