Different exception syntaxes in REST API

[dixonsiu]

Description

When calling Personium's REST APIs different exception syntaxes are returned. It is impossible for App developer to display exception details efficiently.

I think that it is more developer friendly to use unified exception syntax (example).

Unless we clearly stated that certain APIs are OAuth and OAuth exception syntax will be used, etc.

OAuth 2.0 exception

{
    "error_description": "[PR400-AN-0016] - Required parameter [password] missing.",
    "error": "invalid_request"
}

OData exception

{
    "code": "PR404-OD-0001",
    "message":{
        "lang": "en",
        "value": "No such entity set."
   }
}

Personium exception

{
    "code": "PR400-MC-0002",
    "message":{
         "lang": "en",
         "value": "Path based CellUrl access is not allowed."
    }
}

[shimono]

Please propose a unified syntax, that comply with both odata spec and oauth2 spec.