Bug 29002: Fix async bookings load issues

Bug 29002: Fix async bookings load issues

This patch updates the modal booking form to only fire the ajax request
upon first modal opening and then moves the data related setup into a
function that can be trigger either upon promise resolution or
immediately if the data already exists at the time the modal is opened.

We also update some instances of datetime processing to use dayjs
endOf('day') function as it appears to work more reliably with timezone
maths that our prior work that used direct mathematical manipulations.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Janet McGowan <janet.mcgowan@ptfs-europe.com>
Signed-off-by: Caroline Cyr La Rose <caroline.cyr-la-rose@inlibro.com>
Signed-off-by: Laurence Rault <laurence.rault@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>