Include root CAs in spiffe-vault image

Dockerfile

@@ -9,11 +9,15 @@ RUN make build
 
 FROM vault:1.8.2 AS vault-binary
 
-FROM busybox
+FROM alpine:3.14.2 as certs
+RUN apk update && apk add ca-certificates
+
+FROM busybox:1.33.1
 LABEL maintainer="marco.franssen@philips.com"
 RUN mkdir -p /app
 WORKDIR /app
 ENV VAULT_ADDR=
+COPY --from=certs /etc/ssl/certs /etc/ssl/certs
 COPY --from=builder build/bin/spiffe-vault .
 COPY --from=vault-binary bin/vault /usr/local/bin/vault
 ENTRYPOINT [ "/app/spiffe-vault" ]