Pin Docker image rust:buster

rust:buster
->
rust:buster@sha256:f5da153862af6a25fcf49dde3cb19b5b513f78bc00e317eb64e898a66af2881d

 [atomist:generated]
 [atomist-skill:atomist/docker-base-image-policy]

Signed-off-by: Atomist Bot <bot@atomist.com>

react-rust-postgres/backend/Dockerfile

@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1.4
-FROM rust:buster AS base
+FROM rust:buster@sha256:f5da153862af6a25fcf49dde3cb19b5b513f78bc00e317eb64e898a66af2881d AS base
 
 ENV USER=root
 ENV ROCKET_ADDRESS=0.0.0.0