Use the centos base image to embed a system SSL/TLS truststore

Dockerfile

@@ -1,5 +1,15 @@
-FROM scratch
+# We use the centos base image (and not the "scratch" base image) because we need
+# a default trust store (aka SSL/TLS trusted certificates).
+# 
+# If you want to rebuild this image using the "scratch" base image, make sure to mount a 
+# copy of the system truststore at a supported location. 
+# 
+# See :
+#  - https://golang.org/src/crypto/x509/root_unix.go
+#  - https://golang.org/src/crypto/x509/root_linux.go
+FROM centos:centos7
 COPY apicast-sidecar-proxy /apicast-sidecar-proxy
 EXPOSE 9090 9091
 ENTRYPOINT [ "/apicast-sidecar-proxy" ]
+CMD [ ]