Customer is using custom HTTP headers in request and/or response for their reverse proxy setup. They want to add the values of these header into access-log as one of the fields.

This can be performed by using the field "request.x_header.HeaderName" or "response.x_header.HeaderName" in access-log format.

Eg:

request.x_header.X-Test

where "X-Test" is the custom request header used by in request