The groupsClaimMapping setting allows one to specify which claim to pull
group information from the OIDC provider.  Previously it assumed group
information was always in the "groups" claim, but that isn't the case
for many OIDC providers (such as AWS Cognito using the "cognito:groups"
claim instead)

Signed-off-by: Scott Lemmon <slemmon@aurora.tech>
Signed-off-by: Rui Yang <ruiya@vmware.com>