[Appointments] Overview ticket - Setting up appointment slots

When opening the tickets after the mockup, we can work on couple of points in one pr.

• Ability to set default notification time for the appointment event (Björn, Viktor)
• Also allow selecting shared calendars for checking conflicts (Björn)
• Allow adding a custom confirmation message
• Could anything be progressively disclosed?
• Time ranges can be set to your calendar availability first, if unchecked then show everything
• Info button on top of modal explaining what is an appointment
• Save button is not visible at all time
• Prevent ask are you sure before closing on click outside?
• Talk
• Add a different link for each appointment? Other than Talk (Zoom, Jitsi, etc)
• Open Desk project?
• Lobby enabled by default
• Change the string - Clean up Talk rooms a few days after the appointment?
• Archive of past appointments?
• Change string "Create a Talk room" --> "Create a Talk conversation" "Add time before and after..." "Planning restrictions"
• All the dropdowns have different styles
• Everything should be migrated to the calendar component
• Markdown in description field