Add syntax check on for policy attribute values

Add a syntax check for attribute values of PDP checks.

• Review of the expressions in https://github.com/OpenConext/OpenConext-manage/issues/478

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 (configurable in application.yml)
• affiliation: check against the list of known values (configurable in application.yml)
• 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.

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

The best way to implement this seems to be to add configuration to each attribute in allowed_attributes.json, specifying the allowed format (for example, by regular expression). For example,

 {
    "value": "urn:mace:dir:attribute-def:eduPersonAffiliation",
    "label": "Edu person affiliation",
    "validation_regex": "^(student|staff|faculty|employee|member)$"
  }