Pull latest dotnet 6.0-focal image and add Microsoft Signing Keys to avoid expired signature causing deployment failure

[seantleonard]

Purpose

Closes #7

Per #7, I get a deployment error when trying to use the sample because the sample's dockerfile refers to an old image from October 3, 2023:

• https://mcr.microsoft.com/en-us/product/devcontainers/dotnet/tags
  Essentially: hardcoding the image to use 0-6.0-focal pull that specific image. Removing the prefix 0- allows the latest container image to be pulled for dotnet 6 on Ubuntu 20.04 (Focal).

tag	type	digest	date
0-6.0-focal	OCI Image Index	sha256:ec557bf5cb00970cd09488f38b15a9bf488cfb8ab15269174b5882f6b3255e82	10/03/2023

And should be pulling latest:

tag	type	digest	date
6.0-focal	OCI Image Index	sha256:d45a9a129eceb58ce018eced364d29959514ebfb096fcc71a375b719693bf7cb	05/30/2024

Also imports Microsoft signing keys to fix gpg error

# Import Microsoft Signing Keys
# https://learn.microsoft.com/dotnet/core/install/linux-ubuntu#unable-to-locate--some-packages-could-not-be-installed
RUN sudo apt-get install -y gpg wget \
    && wget https://packages.microsoft.com/keys/microsoft.asc \
    && cat microsoft.asc | gpg --dearmor -o microsoft.asc.gpg \
    && sudo mv microsoft.asc.gpg /etc/apt/trusted.gpg.d/ \
    && sudo chown root:root /etc/apt/trusted.gpg.d/microsoft.asc.gpg

Background on failure

The deployment errors out seemingly due to docker-outside-of-docker. Not sure if this is the cause or just a symptom of the failure.

5.546 W: GPG error: https://packages.microsoft.com/ubuntu/20.04/prod focal InRel
ease: The following signatures couldn't be verified because the public key is no
t available: NO_PUBKEY EB3E94ADBE1229CF
5.546 E: The repository 'https://packages.microsoft.com/ubuntu/20.04/prod focal
InRelease' is not signed.
5.547 ERROR: Feature "Docker (docker-outside-of-docker)" (ghcr.io/devcontainers/
features/docker-outside-of-docker) failed to install! Look at the documentation
at https://github.com/devcontainers/features/tree/main/src/docker-outside-of-doc
ker for help troubleshooting this error.

It looks like the docker outside of docker feature install.sh only imports the Microsoft signing keys if Moby is used:
https://github.com/devcontainers/features/blob/414d3450434b9072f01afe80cab226c60088224a/src/docker-outside-of-docker/install.sh#L215-L229

I do notice the Sample project I'm using doesn't provide a Moby property, which per docker outside of docker docs, moby should be true by default. Not sure why the key setup isn't working.

azure-sql-library-app-blazor/.devcontainer/devcontainer.json

Lines 59 to 61 in 0a1ba8c

	"ghcr.io/devcontainers/features/docker-outside-of-docker:1": {
	"version": "latest"
	}

		"ghcr.io/devcontainers/features/docker-outside-of-docker:1": {
			"version": "latest"
		}

Does this introduce a breaking change?

By staying at .net 6 and Ubuntu 20.04 (focal), this is a non-breaking change.

[ ] Yes
[X] No

Pull Request Type

What kind of change does this Pull Request introduce?

[X] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

1. Pull latest code from this commit
2. "Open Folder in Container"
3. Operation should now succeed without signature failure because latest dotnet image is used.

[seantleonard]

Merge #9 in first to see if fixing the pre-req scripts (which also include importing microsoft signing keys) fixes the root of the issue