https://github.com/mattermost/mattermost/issues/28874

Currently, push proxy only supports certificate-based connections to APNs. Description is available at https://docs.mattermost.com/deploy/mobile-hpns.html#host-your-own-push-proxy-service

Token-based authentication to APNs should be used in MPNS: https://developer.apple.com/documentation/usernotifications/establishing-a-token-based-connection-to-apns. Token-based authentication offers a stateless way to communicate with APNs. Stateless communication is faster than certificate-based communication because it doesn’t require APNs to look up the certificate, or other information, related to your provider server. There are other advantages to using token-based authentication.