I am a software engineer at OpsGenie. We have developed an integration specific to Observium. Thus, we would be very pleased if you can fix your integration so that it uses  /v1/json/observium endpoint rather than /v1/json/alert endpoint. Observium Integration works similar to generic Webhook integration but we customised it for Observium. You can check our Observium Integration document for more information which can be found at https://www.opsgenie.com/docs/integrations/observium-integration.