How to build a custom Docker image?

docker build -t dify-sandbox-custom:latest .
Sending build context to Docker daemon 3.072kB
Step 1/8 : FROM python:3.10-slim-bookworm
---> e6d8b768c22f
Step 2/8 : RUN echo "deb http://deb.debian.org/debian testing main" > /etc/apt/sources.list && apt-get update && apt-get install -y --no-install-recommends pkg-config libseccomp-dev wget curl xz-utils zlib1g expat perl libsqlite3-0 && apt-get clean && rm -rf /var/lib/apt/lists/*
---> Running in a5e19f77ee9d
Get:1 http://deb.debian.org/debian testing InRelease [178 kB]
Err:1 http://deb.debian.org/debian testing InRelease
At least one invalid signature was encountered.
Get:2 http://deb.debian.org/debian bookworm InRelease [151 kB]
Err:2 http://deb.debian.org/debian bookworm InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0E98404D386FA1D9 NO_PUBKEY 6ED0E7B82643E131 NO_PUBKEY F8D2585B8783D481
Get:3 http://deb.debian.org/debian bookworm-updates InRelease [55.4 kB]
Err:3 http://deb.debian.org/debian bookworm-updates InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0E98404D386FA1D9 NO_PUBKEY 6ED0E7B82643E131
Get:4 http://deb.debian.org/debian-security bookworm-security InRelease [48.0 kB]
Err:4 http://deb.debian.org/debian-security bookworm-security InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 54404762BBB6E853 NO_PUBKEY BDE6D2B9216EC7A8
Reading package lists...
W: GPG error: http://deb.debian.org/debian testing InRelease: At least one invalid signature was encountered.
E: The repository 'http://deb.debian.org/debian testing InRelease' is not signed.
W: GPG error: http://deb.debian.org/debian bookworm InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0E98404D386FA1D9 NO_PUBKEY 6ED0E7B82643E131 NO_PUBKEY F8D2585B8783D481
E: The repository 'http://deb.debian.org/debian bookworm InRelease' is not signed.
W: GPG error: http://deb.debian.org/debian bookworm-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0E98404D386FA1D9 NO_PUBKEY 6ED0E7B82643E131
E: The repository 'http://deb.debian.org/debian bookworm-updates InRelease' is not signed.
W: GPG error: http://deb.debian.org/debian-security bookworm-security InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 54404762BBB6E853 NO_PUBKEY BDE6D2B9216EC7A8
E: The repository 'http://deb.debian.org/debian-security bookworm-security InRelease' is not signed.
E: Problem executing scripts APT::Update::Post-Invoke 'rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true'
E: Sub-process returned an error code
The command '/bin/sh -c echo "deb http://deb.debian.org/debian testing main" > /etc/apt/sources.list && apt-get update && apt-get install -y --no-install-recommends pkg-config libseccomp-dev wget curl xz-utils zlib1g expat perl libsqlite3-0 && apt-get clean && rm -rf /var/lib/apt/lists/*' returned a non-zero code: 100

Start by reproducing the provided `docker build -t dify-sandbox-custom:latest .` command and inspect Step 2/8, where the Python 3.10 slim Bookworm image runs `apt-get update` against Debian testing and Bookworm repositories. Check the base image's repository and package-signing configuration; done means the custom image builds successfully and installs the listed packages.

Written by the indexing model from the issue text.