[Openid-specs-ab] Issue #1108: Purpose field for claims requests and revving of policy_url (openid/connect)

[Nat]

New issue 1108: Purpose field for claims requests and revving of policy_url
https://bitbucket.org/openid/connect/issues/1108/purpose-field-for-claims-requests-and

Nat Sakimura:

Currently, we are relying on policy\_url for the purpose statement for the claims request. 

We have come some distance since we have defined it and the trend is to making it possible to state per claim purposes when needed. \(see for example ISO/IEC 29184\). 

It might be a good time to consider something like: 

```json
{
  "email":
   {
     "essential": true, 
     "purpose":"to send receipt", 
     "example":"alice at example.com"
    }
}
```