Enhanced ECS function tests

Documentation updates

Also includes re-factoring of some scripts and functions

Issue-ID: NONRTRIC-311

Signed-off-by: BjornMagnussonXA <bjorn.magnusson@est.tech>
Change-Id: I891ab5b093699530c771b3d6177bfc24daae3b1d
diff --git a/test/prodstub/Dockerfile b/test/prodstub/Dockerfile
index bdc3521..4768bf9 100644
--- a/test/prodstub/Dockerfile
+++ b/test/prodstub/Dockerfile
@@ -15,7 +15,9 @@
 #  ============LICENSE_END=================================================
 #
 
-FROM python:3.8-slim-buster
+ARG NEXUS_PROXY_REPO
+
+FROM ${NEXUS_PROXY_REPO}python:3.8-slim-buster
 
 COPY app/ /usr/src/app/
 COPY cert/ /usr/src/app/cert/