nginx-flask-mongo: add dev envs support (#268)

Signed-off-by: Milas Bowman <milas.bowman@docker.com>

nginx-flask-mongo/flask/Dockerfile

@@ -1,7 +1,28 @@
-FROM python:3.7
+# syntax=docker/dockerfile:1.4
+FROM --platform=$BUILDPLATFORM python:3.10-alpine AS builder
 
 WORKDIR /src
-COPY . .
-RUN pip install -r requirements.txt --no-cache-dir
+COPY requirements.txt /src
+RUN --mount=type=cache,target=/root/.cache/pip \
+    pip3 install -r requirements.txt
 
-CMD ["./server.py"]
+COPY . .
+
+CMD ["python3", "server.py"]
+
+FROM builder as dev-envs
+
+RUN <<EOF
+apk update
+apk add git
+EOF
+
+RUN <<EOF
+addgroup -S docker
+adduser -S --shell /bin/bash --ingroup docker vscode
+EOF
+
+# install Docker tools (cli, buildx, compose)
+COPY --from=gloursdocker/docker / /
+
+CMD ["python3", "server.py"]