feat(dev): Document new RequestHeader attribute

Signed-off-by: provokateurin <kate@provokateurin.de>

Author: provokateurin

developer_manual/app_publishing_maintenance/app_upgrade_guide/upgrade_to_32.rst

@@ -41,6 +41,7 @@ Added APIs
 - New method ``\OCP\IUser::canChangeEmail`` allowing to check if the user backend allows the user to change their email address.
 - New method ``\OCP\Files\IFilenameValidator::sanitizeFilename`` allowing to sanitize a given filename to comply with configured constraints.
 - New service ``\OCP\Template\ITemplateManager`` to access template related functions, and get instances of new interface  ``\OCP\Template\ITemplate`` instead of building manually ``\OCP\Template``.
+- New attribute ``\OCP\AppFramework\Http\Attribute\RequestHeader`` used for documenting request headers for OpenAPI specifications generated using openapi-extractor.
 
 Changed APIs
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