Bug 34999: Throw exception for public routes if OPACMaintenance is enabled

Bug 34999: Throw exception for public routes if OPACMaintenance is enabled

Test plan:
[1] Try public endpoint like /api/v1/public/biblios/X/items.
    * Replace X by an existing biblionumber.
    You should receive a 200.
[2] Enable OPACMaintenance. Set to Show.
[3] Try same endpoint. You should get a 503 with a json error.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>