open5gs-latest: add osmocom user for ttcn3-pgw-test

In ttcn3-pgw-test we're running open5gs-upfd as a non-root user.
We do have this user in open5gs-master, but not in open5gs-latest.

Change-Id: I9139fc52fa6973cf495559d3c4202d9f804a2079
Related: OS#5913

open5gs-latest/Dockerfile

@@ -30,3 +30,9 @@ RUN	apt-get update && \
 	apt-get install -y \
 		mongodb-org \
 		open5gs
+
+# create a user
+ARG	username=osmocom
+RUN	useradd -m --uid=1000 ${username} && \
+	echo "${username} ALL=(root) NOPASSWD:ALL" > /etc/sudoers.d/${username} && \
+	chmod 0440 /etc/sudoers.d/${username}