Syntax check on PDP fields

[baszoetekouw]

It would be nice if attribtue values of PDP checks would be syntax checked.

I.e.:

• SURFteams grouop name: make sure it start with urn:collab:group:surfteams.nl:nl:surfnet:diensten
• SAB role: make sure it is a single word like "Infrabeheerder" and maybe even check it against a list of known values
• affiliation: check against the list of known values
• entitlement: check this it is an uri (url or urn)
• scoped-affiliation: make sure it is of form <affiliation>@<domain>
• mail address: make sure it looks like an email address
• schac: make sure it looks like a domain. For bonus points, check that the schachome is defined in a shic-scope for an existing IdP in Manage.

In all cases, show any mismatched in the UI, but allow a user to submit/override "incorrect" values, if they wish. It is very probably that in some cases, we need to send out-of-spec values (for example, undefined affiliations).

Similar to #447, we need to find. a generic way to do this, so these kinds of business rules are not hardcoded in the application.