pin base image to alpine:3.11

docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:latest
+FROM alpine:3.11
 LABEL maintainer="felixlohmeier@opencultureconsulting.com"
 # The OpenRefine Python Client Library from PaulMakepeace provides an interface to communicating with an OpenRefine server. This fork extends the command line interface (CLI) and supports communication between docker containers.
 # Source: https://github.com/opencultureconsulting/openrefine-client