deprecation policy and framework

The policy, and the technical framework which supports it, need to be documented and accepted, before 1.0.

They are closely linked and should really be a unified cEP, as the policy imposes requirements on the implementation.

The most critical task is defining where we are now, at 0.8/9. Are we currently trying to provide a dependable API, or is it still in flux until 1.0?

However, the most important step is demarcating what is public vs private. If that is not clear, there may be parts of the code base that need to be declared non-public, which means the API is still in flux.

A common policy that most people agree with is that `_` prefix means that the object is explicitly not covered by a deprecation policy. A client that invokes a `_` prefixed object has no contract to rely on.

Is *everything* else a part of the public API? If not, do we have a clear definition of what is in the public API?

Start by reviewing the existing cEPs in this repository and the issue's questions about the 0.8/9 API status, public versus private objects, and underscore-prefixed objects. The work is done when a unified cEP documents the deprecation policy and supporting framework, clearly defines the public API, and is accepted before 1.0.

Written by the indexing model from the issue text.