Remove feature to issue isMemberOf value based on guest_qualifier

[thijskh]

EB has a feature that can add a specific URN value (defined in addgueststatus_guestqualifier parameter) to the isMemberOf attribute for an SP, if the IdP of the user has a specific configuration in the coin:guest_qualifier setting.

The global idea is that the SP can determine if this user is a full member of the federation or a guest user.

In short, it works like this, if addgueststatus_guestqualifier is set to urn:collab:org:vm.openconext.org:

guest_qualifier of IdP	Value of isMemberOf released to SP	semantics
None	urn:collab:org:vm.openconext.org	"None" of the users of this IdP are guests = everyone gets the member urn
All	nothing	"All" of the users of this IdP are guests = no-one gets the member urn
Some	based on IdP's sent isMemberOf value	"Some" of the users are guests, trust the IdP to indicate which ones

Also EB has input filtering to prevent IdP's that are Some to send the reserved urn value.

Why remove it:

• The feature is unused by us
• The feature is complex to understand and highly intricate and nonobvious to deployers what to do or how to use it
• The feature is implemented in a legacy way and it would significantly clean up Engine's login processing

[baszoetekouw]

This feature is possibly still used by FCCN. They are investigating.