Bug 22678: Use Koha::Logger for Mojolicious API logger

Bug 22678: Use Koha::Logger for Mojolicious API logger

This patch adds Koha::Logger as the Mojolicious logging object
for the API Mojolicious app.

Test plan:
0. Apply the patch and koha-plack --restart kohadev
1. Add $c->app->log->debug('DEBUG') and
$c->app->log->warn('WARN') to a API controller like
Koha::REST::V1::Libraries
2. koha-plack --restart kohadev
3. Go to the API route tied to that API controller method
4. Look at /var/log/koha/kohadev/api-error.log
5. Note that 'WARN' appears but 'DEBUG' does not

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
[EDIT] Adding a context sub to Koha::Logger to get it working.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>