feat(mail): add options to not add X-Foward header in mail

SoObjects/SOGo/SOGoDomainDefaults.h

@@ -38,6 +38,7 @@
 - (BOOL) mailCustomFromEnabled;
 - (BOOL) mailAuxiliaryUserAccountsEnabled;
 
+- (BOOL) mailDisableXForward;
 - (NSString *) mailDomain;
 - (NSString *) imapServer;
 - (NSString *) sieveServer;

SoObjects/SOGo/SOGoDomainDefaults.m

@@ -106,6 +106,11 @@
   return [self boolForKey: @"SOGoMailAuxiliaryUserAccountsEnabled"];
 }
 
+- (BOOL) mailDisableXForward
+{
+  return [self boolForKey: @"SOGoMailDisableXForward"];
+}
+
 - (NSString *) mailDomain
 {
   return [self stringForKey: @"SOGoMailDomain"];