Option to disable public sharing

[baltaner]

Steps to reproduce

0. users are authenticated by ldap
1. Click on sharing-icon
2. Checkbox to public sharing appears

Expected behaviour

I disabled "Allow users to share by link" in nextcloud configuration
I enabled "Allow apps to use share-API"

I expect that there is no public sharing possible in calendar-app

Actual behaviour

Public sharing is possible!

Server configuration

Operating system:
ubuntu 16.04
Web server:
apache 2.4
Database:
mysql 5.7.18
PHP version:
7.0.18
Server version: (see your admin page)
12.0.0
Calendar version: (see the apps page)
1.5.3

[georgehrke]

Please report in the server repo as well
@tcitworld

[tcitworld]

Fix is coming, writing tests...