chore: reduce number of CVEs in docker image

Signed-off-by: ThibaultFy <[email protected]>

docker/substra-backend/Dockerfile

@@ -5,7 +5,7 @@ ENV PYTHONUNBUFFERED=1
 
 RUN apt-get update -y \
     && apt-get install --no-install-recommends -y --only-upgrade gnupg \
-    && apt-get install --no-install-recommends -y software-properties-common python3.11 python3-pip gcc python3-dev \
+    && apt-get install --no-install-recommends -y software-properties-common python3.11 python3-pip gcc python3-dev ca-certificates \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
@@ -52,7 +52,7 @@ COPY ./backend/dev-requirements.txt /usr/src/app/.
 RUN pip3 install --prefix /usr/local --no-cache-dir -r dev-requirements.txt
 COPY backend/dev-startup.sh .
 
-FROM python:3.11-slim
+FROM ubuntu:22.04
 
 ARG VERSION
 ENV BACKEND_VERSION=${VERSION:-dev}