made pa_job_manager use mythtv:mythtv, but had to hardcode PJM_* vars, I tried to pass them through docker-compose.yml

Dockerfile

@@ -1,5 +1,9 @@
 FROM ubuntu:20.04
 WORKDIR /code
+USER root
+ENV PJM_UID=500
+ENV PJM_GID=500
+RUN groupadd -g ${PJM_GID} mythtv && useradd -r -u ${PJM_UID} -g ${PJM_GID} mythtv
 ENV TZ=Australia/Melbourne
 RUN truncate -s0 /tmp/preseed.cfg && \
        (echo "tzdata tzdata/Areas select Australia" >> /tmp/preseed.cfg) && \