This issue is automatically created based on existing pull request: #39712: Update GraphQL tests Client.php for case-insensitive substring comparation

Description (*)

use case-insensitive comparation for headers

Related Pull Requests

Fixed Issues (if relevant)

1. none

Manual testing scenarios (*)

When some custom graphql tests work with cookies the core client works unexpectedly.
Using case-insensitive substring comparation fixes the problem.

Questions or comments

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)