identity_openid  enable OpenID SSO support

ARGS:
config_url*   (url)       openid discovery document e.g. "https://accounts.google.com/.well-known/openid-configuration"
client_id     (string)    unique public identifier for apps e.g. "292085223830.apps.googleusercontent.com"
claim_name    (string)    JWT canned policy claim name, defaults to "policy"
claim_prefix  (string)    JWT claim namespace prefix e.g. "customer1/"