Fix no-user-in-docker-container-when-using---build-template-condapixiv1

[munishchouhan]

closes #973

Problem

Python's getpass.getuser() was raising OSError: No username set in the environment when running in containers built with the pixi template, but worked fine with the
micromamba template.

Root Cause

The pixi template didn't set the USER environment variable in the final container stage, while Python's getpass.getuser() function requires one of these environment
variables to be present: LOGNAME, USER, LNAME, or USERNAME.

Solution

Updated the pixi Dockerfile template (src/main/resources/templates/conda-pixi-v1/dockerfile-conda-file.txt) to match the micromamba v2 template behavior by adding:

• USER root directive
• ENV USER=root environment variable

This ensures Python applications can successfully call getpass.getuser() without errors.

Changes

• Modified conda-pixi-v1/dockerfile-conda-file.txt to add USER and ENV directives
• Updated all pixi-related tests in TemplateUtilsTest and ContainerHelperTest to reflect the new template output

[munishchouhan]

tested locally with the reprocuder:
#973 (comment)

container: docker.io/hrma017/python_pip_drevalpy:5a2ddde782d035e0

% nextflow run test_container.nf -c docker-user.config

 N E X T F L O W   ~  version 25.11.1-edge

Launching `test_container.nf` [desperate_lamport] DSL2 - revision: cc774c8f10

executor >  local (1)
[31/87ea03] TEST_PYTHON_CONTAINER [100%] 1 of 1 ✔
Completed at: 10-Feb-2026 10:08:11
Duration    : 7m 4s
CPU hours   : 0.1
Succeeded   : 1