Should the concrete classes be hidden?

[ndrwrbgs]

In the java source version, the concrete classes are created by AutoValue which, from my limited understanding, does not expose the concrete types. If we want to preserve that intention, then I'd propose our concrete classes (like BucketBoundaries, should not be sealed, but rather be static with just the Create method, and have private sealed implementation classes.

If the intention is to expose these concrete types (which may result in folks programming to those rather than the intended interfaces) then that's fine too - but at that point we may want to consider if we want to expose interfaces at all.

[SergeyKanzhelev]

This will be handled in OpenTelemetry project