The group claims read from the session cache file are loaded as `[]interface{}` (slice of empty interfaces) so when we previously did a `groups, _ := idTokenClaims[oidc.DownstreamGroupsClaim].([]string)`, then `groups` would always end up nil.
The solution I tried here was to convert the expected value to also be `[]interface{}` so that `require.Equal(t, ...)` does the right thing.
This bug only showed up in our acceptance environnment against Okta, since we don't have any other integration test coverage with IDPs that pass a groups claim.
Signed-off-by: Matt Moyer <moyerm@vmware.com>
