Improve Request Object Usage

[solverat]

• Use $request->files instead of $_FILES
• Use $request->request->get() / $request->query->get() instead of $request->get()

[github-actions]

Thank you for reporting this issue. Since it hasn’t been labeled as “OpenDXP:Priority,” “OpenDXP:ToDo,” or “OpenDXP:Backlog,” we don’t plan to address it in the near future. If this is a bug report, please consider submitting a pull request — we’ll review it as soon as possible. If you’d like to contribute a new feature, please get in touch with us first so we can discuss whether it fits. Thanks for your understanding.

[solverat]

Done with #39