WWW_GROUP_ID : problem with existing groups

[M-Paladin]

The docker host uses a NFS mount with documents and custom stored on it.
I use this directory in the volume for dolibarr
I want to use UID 1001 and GID 100 because I use those IDs in my mount.
In the container, as GID 100 is already used by "users" by default, it cannot be assigned to www-data. In addition, there's a complain in the docker logs when the script has to change ownership.
The mounted volume already has the right user and group, but not for dolibarr.
I don't know if the group is used for anything in dolibarr as I've not used it that much.

services:
  dolibarr:
    image: dolibarr/dolibarr:20.0.3-php8.2
    restart: unless-stopped
    container_name: dolibarr
    volumes:
    - /srv/nfs/config/dolibarr/documents:/var/www/documents
    - /srv/nfs/config/dolibarr/custom:/var/www/html/custom
    ports:
    - 80:80
    environment:
      WWW_USER_ID: "1001"
      WWW_GROUP_ID: "100"

dolibarr  | As UID / GID have changed from default, update ownership for files in /var/ww ...
dolibarr  | chown: changing ownership of '/var/www/html/custom': Operation not permitted
dolibarr  | chown: changing ownership of '/var/www/documents/users/temp': Operation not permitted
dolibarr  | chown: changing ownership of '/var/www/documents/users': Operation not permitted
dolibarr  | chown: changing ownership of '/var/www/documents/stock': Operation not permitted
dolibarr  | chown: changing ownership of '/var/www/documents/expedition/sending': Operation not permitted
dolibarr  | chown: changing ownership of '/var/www/documents/expedition/receipt': Operation not permitted
dolibarr  | chown: changing ownership of '/var/www/documents/expedition': Operation not permitted
...

Is there a chance to have a more flexible approach than this one regarding UID/GID management ?

dolibarr-docker/docker-run.sh

Lines 423 to 437 in d786523

	# Set permission
	local CURRENT_UID=$(id -u www-data)
	local CURRENT_GID=$(id -g www-data)
	usermod -u ${WWW_USER_ID} www-data
	groupmod -g ${WWW_GROUP_ID} www-data
	if [[ ${CURRENT_UID} -ne ${WWW_USER_ID} || ${CURRENT_GID} -ne ${WWW_GROUP_ID} ]]; then
	# Refresh file ownership cause it has changed
	echo "As UID / GID have changed from default, update ownership for files in /var/ww ..."
	chown -R www-data:www-data /var/www
	else
	# Reducing load on init : change ownership only for volumes declared in docker
	echo "Update ownership for files in /var/www/documents ..."
	chown -R www-data:www-data /var/www/documents
	fi