What is the Data Holder (DH) oAuth response when the value of
cdr_arrangement_id in the Pushed Authorisation Requests (PAR) is equal to
null or is an
cdr_arrangement_id should be ignored. The CDS do not require a
cdr_arrangement_id to be presented in the request object.
The behaviour for an
empty string is not defined by the CDS, however it may be ignored.
A 400 Bad Request error with
invalid_request as the title would be appropriate. The DH may provide further details in the oAuth error response including the CDR error code