[videoreserves] Add monitoring in CheckMK for videoreserves

[maxkadel]

What maintenance needs to be done?

So that we know when videoreserves goes down before users report issues, we need to add monitoring.

The last incident we had, the page was returning as a 200, but was actually showing the literal code, rather than the video player (see #5457).

Level of urgency

• High
• Moderate
• Low

Why is this maintenance needed?

• A clear description of why this is needed.

Acceptance criteria

• We get a push notification when video reserves is not rendering / is serving up the PHP script text
• We get a push notification when video reserves is not sending people to CAS (this is a stretch goal and can be split into its own ticket)
• [ ]

Implementation notes, if any

• For rendering, we might be able to check for some of the text on the page, e.g. "Assigned audio and video materials are made available only to the students...", rather than trying to check for the video player.
• We might also be able to check that the PHP script text is not present, e.g. include('../../vendor/autoload.php');
• For checking CAS, we might check that https://videoreserves-prod.princeton.edu/hrc/vod/clip.php returns a 302 (redirect to CAS), we would just want to be sure that we do not follow the redirect, so we don't have issues with the campus IDP service