I found that (since 1.9.2?) there's RealmResourceProvider that gives me the possibility to provide own REST endpoint. After implementing the endpoint using async capabilty of jax-rs, I'm getting exception like: 

UT010026: Async is not supported for this request, as not all filters or Servlets were marked as supporting async.

How is it possible to tweak Keycloak (I'm currently on 1.9.3) to asynchronously respond to my requests in implementation of RealmResourceProvider?

Thank you for any comment on this.

Best regards,

Bystrik