[FIX] Auth: Prevent resetting mail options for ECS users

[mjansenDatabay]

If approved, the change has to be picked to all maintained branches.

[smeyer-ilias]

Hi @mjansenDatabay the forcement of ilMailOptions::INCOMING_LOCAL has been introduced since ECS user accounts are able to authenticate on the installation which hosts the ECS content.
To access the content, they must always access the ECS shares via the platform on which the content was shared. If they receive emails stating 'You have been enrolled in course XY' they are unable to use the permanent link.

[mjansenDatabay]

Hi @mjansenDatabay the forcement of ilMailOptions::INCOMING_LOCAL has been introduced since ECS user accounts are able to authenticate on the installation which hosts the ECS content. To access the content, they must always access the ECS shares via the platform on which the content was shared. If they receive emails stating 'You have been enrolled in course XY' they are unable to use the permanent link.

Thx Stefan, I am aware of this. The ECS authorities just had a meeting and discussed this. It is planned to create a mapping resource (between source and target resources) which then can be used to re-write permanent links for ECS users.

I should have made this PR "WIP", since this is only one part of the change they want to make.