I've revised my question. What I would really like to do is rewrite / transform the value of any response header.
Is there a way to do that with Traefik?
Just noticed this in the docs...
...which explains why I couldn't set multiple cookies using customResponseHeaders.
I can't find a way to set cookies in the response. Anyone know of a way?
My immediate need is simply to set the domain for cookies in the response, which seems pretty straightforward to do in nginx via the proxy_cookie_domain directive of the ngx_http_proxy_module module.
Is there a way to achieve the same result with Traefik?