Add Dockerfile for kanboard.

infra-cluster/kanboard/images/Dockerfile

@@ -0,0 +1,7 @@
+FROM docker.io/library/debian:bullseye as builder
+
+RUN apt update -y && apt install -y git
+RUN git clone https://github.com/kanboard/plugin-oauth2.git
+
+FROM docker.io/kanboard/kanboard:latest
+COPY --from=builder /plugin-oauth2 /var/www/app/plugins/OAuth2