Allow members to contact their Team Leader through Tapir when they cannot attend a shift

[seuribe]

Background
When a member cannot make it to a shift, they should contact their Team Leader (if there is one for that shift) to let them know. But there is currently no easy, direct way of doing it, unless the Team Leader has previously given them some contact information. This leads to Leaders not knowing that people will not show up, which could be avoided (at least in some cases), if Tapir provided some easy way to accomplish it.

This is a reworked version of Issue #380, after receiving feedback from the Teamleitung.

Proposal
Users will be allowed to mark their shifts as "not attending" in the last 48 hours. This will not remove them from the shift, nor mark it as looking for a replacement. If the absence is justified, members still need to communicate with the member office.

Implementation
Currently, there are two buttons for disengaging with a shift: "look for a replacement" and "unregister myself".

A third button will be available only in the last 48 hours, for notifying the absence from the shift. This button will flag the shift as "not attending" in the attendance column.

References
Discussion in slack https://supercoopberlin.slack.com/archives/C01SYB5QSTB/p1670234519085399

[crosspolar]

I would rather change the "Look for a stand-in" button to "Look for a stand-in and mark myself as not attending", to not create confusion between those. Plus a little help-pop-up to explain the button.

[Theophile-Madet]

How about a single button that always does the best possible option for the member?
It could say "I can't attend : ACTION", for example "I can't attend : look for a stand-in". Hovering over it could explain the rules,
and clicking it could lead to a confirmation page that recapitulates the rules.

• If more than 7 days before the shift and not and ABCD-shift : unregister the user
• Else, if more than 2 days before the shift : look for a stand-in
• Else : mark as not attending

[crosspolar]

Is it planned that when it's less than 2 days left, the member can mark itself as not attending plus still search for a last-minute-stand-in?

[seuribe]

@crosspolar I've asked the Mitgliederbüro about the "ask for stand-in in the last 2 days" but still no answer.
@Theophile-Madet I do like your proposal, and I also think about how to avoid multiple buttons where only one would suffice. I wonder if it's not just our programmers brain trying to optimize things, the one talking, ;) and worry that non computer-savvy users might find it more difficult. Maybe not. My idea was to have a first implementation that does the function, and then optimize when we learn how is it working. Also, hovering would not work on mobile, right? (apropos, do we know how many users are active on mobile vs. desktop?)
But there are also cases not covered by that example. If I first look for a stand in, it does not mean that I will not attend, just that I might not. The final button gives teamleaders the confirmation that this will in fact not happen. That's why the meaning of the additional button is different from the "looking for stand in". I'll work some diagrams and share them, to try to make this discussion more graphical. :)

[seuribe]

Latest version of the proposed change

[seuribe]

Same, as a pseudo-state machine, showing which buttons would be available when, and in which state they should leave the shift

[Theophile-Madet]

Replaced with #597 and #607