Get UserInfo in JWT format

[JaykobJ]

Is your feature request related to a problem? Please describe.

Current implementation on getting UserInfo data form /userinfo endpoint only support for fetching data in JSON format. In Keycloak it is possible to also receive UserInfo in JWT format.
This can be configured at client -> advanced options -> under "Fine grain OpenID Connect configuration" set value for "User info signed response algorithm".
Currently if the UserInfo data is set to be JWT, then gocloak returns error since the response is invalid JSON format.

Describe the solution you'd like
I found that the issue is in GetRawUserInfo functions SetResult(&result) call. It tries to unmarshal the response but fails since it is getting a non JSON object in the response.

It would be nice if the GetRawUserInfo function could handle both JSON and JWT UserInfo formats.