Docker: Launch the php image with a non root user

[J3m5]

API Platform version(s) affected: 2.6.3

Description
I tried to launch the php docker image with a non root user but I'm facing problems.
I added the instruction USER www-data at the end of the api-platform-php stage of the dockerfile, (this user is created in the original php-fpm-alpine image),
but then I get permission errors with the commands executed in the docker-entrypoint.sh file.

I tried to change the permissions of the php and composer bin, api/var files etc but it didn't works.

How to reproduce
Run docker-compose with the www-data user set in the dockerfile or in the php service of the docker-compose file.

Additional Context
Configuring and running the containers with a non root user is a requirement from our web host.
The images are meant to be running in a kubernetes environment hosted and managed by a certified health data host.

[J3m5]

I've managed to get it working, the whole stack is running with a non root user now.
I'll post our setup here soon.