Meqaris
Booking/reservation of meeting rooms/equipment with e-mail invitations
...Especially useful in corporate environments, but can be used for anything in general, even by individual users.
Simply add "resource participants" to the recipient list (just like other attendees) of your e-mail invitation to book the resource and wait for a response.
See the project homepage https://meqaris.sourceforge.io and the project Wiki in the menu above.