- Removes `username` and `apiKey` from form data to prevent errors
from the LanguageTool server when these fields are present
- Updates test cases to reflect the new handling of form data bodies
- Switch API key validation to use POST body parameters
- Add support for `application/x-www-form-urlencoded` content type
- Store parsed body in context state for further use
- Reject unsupported content types with 415 status
- Add tests to validate ltProxyAuth behavior for valid, invalid, and missing API keys
- Add tests to verify ltProxyHandler correctly proxies requests and returns responses
