Pass custom Headers to endpoint created using svix

[PurvaSatish]

I am using Svix 1.23.0 version, I need to add a header along with payload to send webhooks, Is there a way to send custom header along with webhooks here.
svix.message.create(
applicationId, MessageIn(
eventType = eventType, payload = convertToMap(orderPayload), eventId = eventId
),
options = PostOptions().idempotencyKey(eventId)
)
I need to send auth token generated by us not using svix while sending webhooks

[svix-jplatte]

You can send additional headers by adding them to the endpoint before sending the message (see https://api.svix.com/docs#tag/Endpoint/operation/v1.endpoint.update-headers).

If you want to send different values per messages, that's not currently supported in the OSS version - if I understood the question correctly you are self-hosting the open source Svix server, right?