feat: Replace generated DH params with RFC 7919 standardized DHE groups

- While the anonymous VOLUME can be dropped from Dockerfile, the path needs to be valid at run-time, might as well ensure it's available by creating the dhparam folder at build.

- Generation logic no longer necessary, dropped. 

- Standardized RFC 7919 groups added (2048, 3072, 4096), with 4096-bit remaining the default size. The DH logic can live in the entrypoint script as well. 

- Third-party supplied pre-generated DH params removed as they're not considered trustworthy compared to RFC 7919 groups.

Dockerfile

@@ -51,7 +51,8 @@ RUN apt-get update \
 # Configure Nginx and apply fix for very long server names
 RUN echo "daemon off;" >> /etc/nginx/nginx.conf \
    && sed -i 's/worker_processes  1/worker_processes  auto/' /etc/nginx/nginx.conf \
-   && sed -i 's/worker_connections  1024/worker_connections  10240/' /etc/nginx/nginx.conf
+   && sed -i 's/worker_connections  1024/worker_connections  10240/' /etc/nginx/nginx.conf \
+   && mkdir -p '/etc/nginx/dhparam'
 
 # Install Forego + docker-gen
 COPY --from=forego /usr/local/bin/forego /usr/local/bin/forego
@@ -69,7 +70,7 @@ WORKDIR /app/
 
 ENV DOCKER_HOST unix:///tmp/docker.sock
 
-VOLUME ["/etc/nginx/certs", "/etc/nginx/dhparam"]
+VOLUME ["/etc/nginx/certs"]
 
 ENTRYPOINT ["/app/docker-entrypoint.sh"]
 CMD ["forego", "start", "-r"]