Bug 11647: require that user log into OPAC to request email subscription notifications

Bug 11647: require that user log into OPAC to request email subscription notifications

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: remy juliette <remy.gonzalves@iepg.fr>
Signed-off-by: Aurelie Fichot <aurelie.fichot@iepg.fr>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes QA script and tests.
Instead of hiding the feature completely, now a message
tells the user to login to subscribe to the email
notifications.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 6310c992bf23d164f013ead7c0b2182226279454)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>