set up API versioning machinery for most internal services

[iliana]

Part of #8727 (the easy ones)

[davepacheco]

I'd expect to see changes for three progenitor client packages that aren't here:

• ntp-admin
• sled-agent
• oximeter

[davepacheco]

We had talked about versioning the three Clickhouse services separately in separate modules. Did you opt not to?

[iliana]

Yeah. I added a note in this block (just below here) suggesting that whoever finds a need to add a new version to these APIs should determine whether all the services should share the same versions, or whether to split them into modules. Although now a couple of days later I'm questioning my choices.

[davepacheco]

We also need to update the server implementations to actually process the version field. I think that's not critical for R17 but if you don't do it now, could you file a new issue for that and make sure it gets the "important non-blocker" status? (this is in the "deliverable" field of the Reconfigurator project)

Edit: to be clear, that's a change like this:

omicron/dns-server/src/lib.rs

Lines 98 to 105 in 811ee9a

	.version_policy(dropshot::VersionPolicy::Dynamic(Box::new(
	dropshot::ClientSpecifiesVersionInHeader::new(
	"api-version"
	.parse::<http::header::HeaderName>()
	.expect("api-version is a valid header name"),
	dns_server_api::VERSION_SOA_AND_NS,
	),
	)))

If it's easy, that would be nice to do now because it'll be easy to forget later and that will break things.

[davepacheco]

Looks good! Some test failures, though.

[iliana]

The test failures are due to the gateway tests not sending an api-version header in any of its requests, which is difficult to do with dropshot::test_util::ClientTestContext. I'm going to back out the gateway API versioning in this PR and add it in a future PR which refactors the tests.