[default values] Send client version via User-Agent header

[cbb330]

Problem

We're rolling out strip protection for default-value tables: the server blocks commits that would silently drop a column's declared default. The guard decides from the committed schema — not from the client version.

To expand it safely from a pilot group to the whole datalake, we need to watch which client versions are committing, to track two signals:

• failures from non-supported clients hitting the guard;
• commits from non-supported clients that slip through it.

The version is observability only; it never gates a commit.

This PR (observability only)

This does not prevent stripping and is not an input to any guard; it makes the client version reliable to read so those two signals can be measured. The OpenHouse Java client now sets an explicit User-Agent: openhouse-java-client/<version> on every outbound request, set once in the shared WebClientFactory.getWebClient() so the tables, jobs, and housetables clients are all covered. Version resolves:

1. an explicit setClientVersion(...) override,
2. the secureclient jar manifest Implementation-Version,
3. "unknown".

build.gradle stamps Implementation-Version into the jar manifest so the fallback is meaningful in packaged builds.

The OpenHouseCatalog now also reads a client-version catalog property and calls setClientVersion(...) (next to its existing client-name handling), so consumers set the version via a property rather than touching the relocated/compileOnly factory directly. li-openhouse#2147 sets that property from the build-time-baked runtime version.

The OpenHouseCatalog also reads a client-version catalog property and calls setClientVersion(...) (next to its existing client-name handling), so consumers set the version via a property instead of touching the relocated/compileOnly factory directly. li-openhouse#2147 sets that property from the build-time-baked runtime version.

Why not rely on the transport's default

Previously these requests carried reactor-netty's default User-Agent: ReactorNetty/<version>, where <version> is getImplementationVersion() on whatever jar provides reactor-netty's classes. That depends entirely on how the OpenHouse client is packaged, so one token means different things:

• thin Java runtime (reactor-netty resolved as a normal dependency, not shaded) → reactor-netty's own transport version (e.g. 1.0.x) — never the OpenHouse client's;
• shaded Spark runtime (reactor-netty bundled un-relocated into the runtime fat jar) → that fat jar's Implementation-Version, i.e. the runtime's version — or, if the fat jar carries no version, nothing (ReactorNetty/dev).

So you can't tell what a ReactorNetty/<version> even refers to, and the thin runtime never reports the OpenHouse version at all. Setting our own openhouse-java-client/<version> User-Agent makes it explicit and unambiguous across both packagings. For shaded runtimes, callers should additionally pass an explicit setClientVersion(...), since jar-manifest introspection is unreliable once shaded.

Testing

• Added TablesApiClientFactoryTest.testSetClientVersionCalled.
• :client:secureclient:test and :client:secureclient:spotlessCheck pass.

Follow-ups (separate changes)

• Consume the header server-side (metric tag / per-commit audit dimension).
• Populate X-Client-Name (engine/app), which the server already reads for the client_name metric.