Required attributes in metadata as default setting for ARP

[maartenk]

In (EDUgain) metadata the 'required attributes' provide the request for required attributes. Currently these values are ignored and the ARP is set by hand.

Request to use the 'required attributes' as proposed vallues for the ARP (in order to prevent manual misconfiguration).

[lucasvanlierop]

@pmeulen / @thijskh would this be a reasonable Janus feature? If so @maartenk would you please create a Janus issue for it?

[maartenk]

See janus-ssp/janus#522