Mark saved objects import/export API stable

[rudolf]

The saved objects import/export APIs are currently still marked as experimental https://www.elastic.co/guide/en/kibana/current/dashboard-import-api.html

We should prioritise making these APIs stable to give users the confidence that they can depend on them.

Blocked on:

• Use snake case for saved objects import/export API #54123
• [Docs] Clarify that payload of import/export APIs should be treated as opaque #159453

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)

[rudolf]

In #54123 (comment) we decided to postpone further work on making the API stable. But I don't think we should block making this API stable until we have a solution to psuedo-copies #91615 (comment)

This is partly because solving psuedo-copies has not been a priority and the timelines are unclear. In addition, even if we decide we need to make a breaking change we have very high adoption of this API. So even if officially marked as preview, in reality we would not be able to make a breaking change to this API, so effectively based on the existing adoption this API should already be treated as "public".

[pgayvallet]

Blocked on: #54123

One of the first issue I remember the team spending lot of time and discussions on 😅 .

But yeah, I agree that in practice, we wouldn't really be able to introduce breaking changes to the current version of this API, given the overall adoption.

However, with the versioned routes / router, we now have a solution to introduce changes such as the ones in #54123, right? So I think we're even more fine moving the APIs (import and export) as stable in their current state?

[lukeelmers]

Supersedes #90429