change session_cookie_samesite setting to something more secure

[goapunk]

Was needed for the servicekonto which is now gone, so we can use something more secure

[CarolingerSeilchenspringer]

@goapunk what is the prio here? should that be done before next release or rather nice to have?

[goapunk]

@CarolingerSeilchenspringer It's very simple so I think we could do it before the next release, will leave it up to you though

[CarolingerSeilchenspringer]

@goapunk then lets do it!