feat(core): Add SOGoDisableSharing option to disable sharing for mail, contacts and calendar

SoObjects/SOGo/SOGoSystemDefaults.h

@@ -22,6 +22,11 @@
 #define SOGOSYSTEMDEFAULTS_H
 
 #import <SOGo/SOGoDomainDefaults.h>
+#import <SOGo/NSString+Utilities.h>
+
+static const NSString *kDisableSharingMail = @"Mail";
+static const NSString *kDisableSharingContacts = @"Contacts";
+static const NSString *kDisableSharingCalendar = @"Calendar";
 
 @interface SOGoSystemDefaults : SOGoDomainDefaults
 {
@@ -121,6 +126,8 @@
 - (NSArray *) passwordRecoveryDomains;
 - (NSString *) JWTSecret;
 
+- (NSArray *) disableSharing;
+
 @end
 
 #endif /* SOGOSYSTEMDEFAULTS_H */