feat: Shift schedule page

[ZeroWave022]

A shift schedule page with the following features is required:

• A calendar
• An overview of who is registered for each of the dates in the calendar
• Possibility to register a shift, and communicate the backend API to get this registered
• Possibility to remove a shift
• Ability to clear the whole calendar if needed, but this needs to be locked behind some kind of permission - perhaps a role assigned to the user (this may require a separate PR as a future date)

Feel free to mention this issue in PRs, but do not close this issue until all of the tasks above have been completed.

Is something missing from the list? Edit this comment if you can, otherwise comment below.

[michaelbrusegard]

Icons are not part of this issue, they will look like this