Currently some users use this way to 'extend' their reservation. Which is pretty smart, but would be better to add a proper way to extend a reservation.

• Prevent creating a reservation if there is still a reservation in the future which hasn't been cancelled
• Show error message with instruction to send email for prolonging reservation
• Move contact email address from pocketbase env to location config
• Add e2e testing to verify this use-case

Contact settings

// General 'mailto:' link or link to contact page for this instance
leihbase.contact_link

// Contact email for this location
location.contact_link
// E-mail address over which reservations are managed
location.reservations_email