Pin Docker image python:3.10-alpine

--platform=$BUILDPLATFORM
->
python:3.10-alpine@sha256:c9d3c11e89887c82efeb4f4fee8771a406cf42f41aebbd23148906d5fe3c1426

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

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

flask/app/Dockerfile

@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1.4
-FROM --platform=$BUILDPLATFORM python:3.10-alpine AS builder
+FROM --platform=$BUILDPLATFORM python:3.10-alpine@sha256:c9d3c11e89887c82efeb4f4fee8771a406cf42f41aebbd23148906d5fe3c1426 AS builder
 
 WORKDIR /app