setup automated Keycloak image builds with Woodpecker, kaniko and crane

This way the Keycloak host can simply pull a finished image and doesn't
need to build a Keycloak image itself.

Co-authored-by: c6ristian <c6ristian@christian.moe>

keycloak/Containerfile

@@ -0,0 +1,14 @@
+ARG TAG=latest
+FROM quay.io/keycloak/keycloak:${TAG} as builder
+
+ENV KC_DB=postgres
+
+WORKDIR /opt/keycloak
+RUN /opt/keycloak/bin/kc.sh build
+
+FROM quay.io/keycloak/keycloak:${TAG}
+COPY --from=builder /opt/keycloak/ /opt/keycloak/
+
+# Runtime options to be set in compose directly.
+
+ENTRYPOINT ["/opt/keycloak/bin/kc.sh"]