Bug 32991: Add a confirmation message

Bug 32991: Add a confirmation message

Looks easier to have a separate variable for the confirmation box, and
easier for styling as well.

Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Agustín Moyano <agustinmoyano@theke.io>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 754c9f2862c63bdfc03a432e498b1b68d4c0c856)
Signed-off-by: Jacob O'Mara <jacob.omara@ptfs-europe.com>