Security improvements to the LTI integration and the API, an upgraded rich text editor, a fix for resuming a retake via LTI, and security patches for external dependencies.

[Admin] Rich text editor upgrade - The editor used for exam instructions and other formatted content has been upgraded to a newer, supported version. Rich text is now also sanitized on the server before it is saved and displayed, so unsupported or unsafe formatting may be removed.

[LTI] Fix resuming a retake after an LTI launch - Students who start a retake through an LTI integration now correctly resume their session.

[Security] Improvements to the LTI integration and the API and various security patches of external dependencies.