Make batch opt-in more expressive.

[TimothyBJacobs]

Description

This let's people opt-in to a specific version of batching, and allows us to
introduce in the future further flags to customize behavior.

How has this been tested?

Manually tested.

Types of changes

Breaking change to __experimental feature.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[spacedmonkey]

Can you explain a little more about this change? I am not sure I like merged experimental features into core. WordPress doesn't have private API. Once it is core, people will you it.

[TimothyBJacobs]

This is to allow for versioning of the opt-in and provide additional flags for future features. So instead of having a simple true/false we have an expressive array.

Whether the endpoint ships as __experimental/batch or v1/batch is a separate conversation.

[spacedmonkey]

That is confusing with the naming of __experimental of the key. Can we name this something different?

[TimothyBJacobs]

It is named __experimental to match the current version of the batch endpoint.

[draganescu]

Tested this locally and works as expected. I wonder @TimothyBJacobs do we opt in to API versions anywhere else? I wonder if experimental opt in is just yes/no.

Nevertheless the idea to opt in to experimental is good!

[TimothyBJacobs]

I wonder @TimothyBJacobs do we opt in to API versions anywhere else? I wonder if experimental opt in is just yes/no.

We historically don't version APIs at all. We try to support the old format in the new form of the endpoint. This is future proofing in the case that we do end up needing to do that which I think is more likely with the REST API. That's why we have the version in the route after all.

[spacedmonkey]

I do not believe the format of this is correct. I don't want anything in WordPress core marked __experimental.

It can remain in the plugin, but should be changed before going into core.

[TimothyBJacobs]

Naming can be discussed in the Core ticket, https://core.trac.wordpress.org/ticket/50244. If we decide to use v1 we'll just be changing the flag name from __experimental to v1 in turn.