client: lib_docker: add USER/WORKDIR to finalize Dockerfile

Guarantees that any additions to custom Dockerfile (or a missing custom)
will not prevent bringing `up` a container into the correct environment.

client/src/docker/lib/internal/lib_docker.bash

@@ -290,6 +290,16 @@ function lib_docker::__build()
       "$global_custom_dockerfile" >>"$_final" || return $?
   fi
 
+  #
+  # Finalize Dockerfile
+  #
+
+  # Guarantees that any additions to custom Dockerfile (or a missing custom)
+  # will not prevent bringing `up` a container into the correct environment.
+  lib_utils::print_debug "Finalizing '${_final}'"
+  echo -e "# WARNING: keep at end of file\nUSER ${DOCKER_FINANCE_USER}\nWORKDIR /home/${DOCKER_FINANCE_USER}\n" \
+    >>"$_final"
+
   #
   # Execute
   #