server
{
    listen       80;
    server_name  localhost;

    resolver 127.0.0.11:53;  # Docker-DNS. Needed for proxy_pass with variables inside!

    set $MY_SCHEME https;
    set $MY_HOST www.your-website.com;
    set $ziel "${MY_SCHEME}://${MY_HOST}";

    location /
    {
        rewrite_by_lua_block
        {
            local map = {
                GET = ngx.HTTP_GET,
                POST = ngx.HTTP_POST,
            }
            ngx.req.read_body()
            local res = ngx.location.capture('/redirect_checker' .. ngx.var.request_uri, {
                method = map[ngx.var.request_method],
                body = ngx.var.request_body
            })
            -- Detect/change redirect...
            local redirect_target = res.header.Location
            if redirect_target and res.status > 300 and res.status < 309 then
                -- ngx.log(ngx.ALERT, 'redirect_target: '..redirect_target)
                local redirect_target_changed, n, err = ngx.re.gsub(redirect_target, '^https?[:][/][/][^/]+', ngx.var.ziel)
                -- ngx.log(ngx.ALERT, 'redirect_target_changed: '..redirect_target_changed)
                return ngx.redirect(redirect_target_changed, 303)
            elseif res.status == 500 then
                return ngx.exit(500)
            else
                ngx.exec('@backend1')
                return ngx.exit(ngx.HTTP_OK)
            end
        }
    }

    location ~ ^/redirect_checker(.*)$
    {
        # ...
        proxy_pass http://backend1:80$1$is_args$args;
        # ...
    }

    location @backend1
    {
        # ...
        proxy_pass http://backend1:80$request_uri;
        # ...
    }
}

FROM ubuntu:18.04
LABEL maintainer="Ob Rzwo <obr2pd@gmail.com>"
ARG HTTP_PROXY
ENV HTTP_PROXY ${HTTP_PROXY}
ARG HTTPS_PROXY
ENV HTTPS_PROXY ${HTTPS_PROXY}
ARG NO_PROXY
ENV NO_PROXY ${NO_PROXY}
ENV http_proxy ${HTTP_PROXY}
ENV https_proxy ${HTTPS_PROXY}
ENV no_proxy ${NO_PROXY}
RUN touch /etc/apt/apt.conf
RUN apt-get update \
    && DEBIAN_FRONTEND=noninteractive apt-get install --yes --no-install-recommends \
        iproute2 \
        mc \
        mlocate \
        nginx-extras \
        tcpflow \
        vim \
    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
RUN ln -sf /dev/stdout /var/log/nginx/access.log && ln -sf /dev/stdout /var/log/nginx/error.log
EXPOSE 80
STOPSIGNAL SIGTERM
CMD ["nginx", "-g", "daemon off;"]

version: "3"
services:
    dings:
        build:
            args:
                HTTP_PROXY: ${HTTP_PROXY}
                HTTPS_PROXY: ${HTTPS_PROXY}
                NO_PROXY: ${NO_PROXY}
            context: ./dings/
        # image: nginx:1.17.6
        # networks:
            # blah:
        ports:
            - 80:80
        volumes:
            - ./dings/nginx_default.conf:/etc/nginx/sites-available/default