[Openid-specs-ab] Issue #1604: HTTP return code 202 for deferred issuance (openid/connect)

[Thomas Bellebaum]

New issue 1604: HTTP return code 202 for deferred issuance
https://bitbucket.org/openid/connect/issues/1604/http-return-code-202-for-deferred-issuance

Thomas Bellebaum:

When a request for a credential cannot be decided upon and issued right away, the credential endpoint is releasing an `acceptance_token` and asking the client to check back later.  
  
HTTP actually has a status code for this \([reference](https://www.rfc-editor.org/rfc/rfc2616.html#section-10.2.3)\):

> 202 Accepted

I think it makes sense to use it here