[internal-dns] First pass at integrating service discovery codebase

[smklein]

Ports https://github.com/davepacheco/toy-dns into Omicron as internal-dns:

• https://github.com/davepacheco/toy-dns/blob/main/src/client.rs -> internal-dns-client, so clients can depend on the bindings without depending on the server
• https://github.com/davepacheco/toy-dns/tree/main/src -> internal-dns, which holds the server library, binary, and API generator. The "toyadm" interface has, for the moment, been removed.
• https://github.com/davepacheco/toy-dns/tree/main/tests -> internal-dns/tests. Also adds a test for the generated OpenAPI file, and makes some minor tweaks via serde(rename) to ensure it passes our linter.

[davepacheco]

Thanks for doing this! CC @rcgoodfellow.

I think it's worth keeping the CLI tool. Maybe make it a binary in internal-dns-client?

[smklein]

I think it's worth keeping the CLI tool. Maybe make it a binary in internal-dns-client?

Done, added as dnsadm

[davepacheco]

I haven't really reviewed most of the code here. But at this point I think the risk is low and urgency is important -- we should land this so we can make forward progress on the things that need it.

[rcgoodfellow]

The prototype also as a testing workflow that runs the automated tests if you want to pick that up.

• https://github.com/davepacheco/toy-dns/blob/main/.github/workflows/rust.yml

[rcgoodfellow]

LGTM!

[smklein]

The prototype also as a testing workflow that runs the automated tests if you want to pick that up.

• https://github.com/davepacheco/toy-dns/blob/main/.github/workflows/rust.yml

I did port the tests over, but Omicron has its own automation that should be running them: https://github.com/oxidecomputer/omicron/blob/main/.github/workflows/rust.yml