* Support JSON lists for Okta user groups+policies.
Migrate the manually-parsed comma-separated string field types for user
groups and user policies to TypeCommaStringSlice. This means user
endpoints now accept proper lists as input for these fields in addition
to comma-separated string values. The value for reads remains a list.
Update the Okta API documentation for users and groups to reflect that
both user group and user/group policy fields are list-valued.
Update the Okta acceptance tests to cover passing a list value for the
user policy field, and require the OKTA_API_TOKEN env var to be set
(required for the "everyone" policy tests to pass).
* Fix typo, add comma-separated docs.
* Compare groups case-insensitively at login time, since Okta groups are
case-insensitive but preserving.
* Make other group operations case-preserving but otherwise
case-insensitive. New groups will be written in lowercase.
