Enable integration tests with Daphne Helper

[cjpatton]

Partially addresses #2389.

Also, remove code for testing against Daphne running locally.

[cjpatton]

Reviewer note: This tag was created manually. It matches the commit that was checked out when the image was built. In the future we will add publishing the container to CI.

[cjpatton]

@branlwyd can you take a look at the CI failure? It's a bit cryptic:

[inahga]

It actually failed a test further above--this job step just fails the job if a failure as detected earlier. The true error is here https://github.com/divviup/janus/actions/runs/8744950821/job/23999640943?pr=3030#step:14:411, where it complains:

Error response from daemon: Could not find the file /logs in container 99f04f6724ae4b56b30a8a6185505212813810d3c83e31fbc0ccb1d92821b183
thread 'daphne::janus_in_process_daphne' panicked at library/core/src/panicking.rs:144:5:
thread 'daphne::janus_in_process_daphne' panicked at /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/testcontainers-0.15.0/src/core/container.rs:143:17:
container 99f04f6724ae4b56b30a8a6185505212813810d3c83e31fbc0ccb1d92821b183 does not expose port 8788

n.b. I think the second does not expose port 8788 is the true error, and the container logs guard is inducing a double-panic because the container doesn't actually exist at the time of drop.

[divergentdave]

The actual error message is a couple steps above, container <hash> does not expose port 8788, but that's misleading. I tried running the container, and I get the following:

WARNING: The requested image's platform (linux/arm64) does not match the detected host platform (linux/amd64/v4) and no specific platform was requested
exec /bin/bash: exec format error

Unpacking the image, I see that both /bin/bash and /service are indeed ELF executables for ARM aarch64, so this is just an issue with missing images for Intel architectures.

[inahga]

Ah, nice find. Yeah if you built it locally with docker build on an ARM macbook it's going to yield a linux/arm64 image. Perhaps the best way around that is to set an explicit target in Daphne's build step cargo build --target x86_64-unknown-linux-gnu.

[divergentdave]

I don't think it would be worth hardcoding a target in the Dockerfile, since the whole base image needs to match the architecture as well, and whatever (docker-)machine is used for building needs to be able to run that architecture.

[inahga]

Ah right, Rust cross-compilation is not as fool-proof as I had hoped, you still need a platform-specific linker.

[tgeoghegan]

AFAIK Daphne does not support current DAP versions so it doesn't help much to test against it. We can revisit this change if and when Daphne is prepared to test against current Janus versions again.