Support profiles with nested fields

[frafra]

Hi,
some providers do not reply with a flat JSON; for example, dataporten.no has a /userinfo endpoint where the user's details are stored under user:

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8

{
    "user": {
        "userid": "...",
        "userid_sec": ["feide:..."],
        "name": "...",
        "email": "...",
        "profilephoto": "p:..."
    },
    "audience": "..."
}

Source: https://docs.feide.no/developer_oauth/technical_details/oauth_authentication.html

The user_json function assumes a flat JSON instead:

ckanext-oauth2/ckanext/oauth2/oauth2.py

Lines 173 to 175 in e68dd26

	def user_json(self, user_data):
	email = user_data[self.profile_api_mail_field]
	user_name = user_data[self.profile_api_user_field]

I made a workaround for that, but it is not a generic fix: NINAnor@f86448f

[frafra]

Any feedback on that?