A new route is introduced, `batch/v1`, that accepts a list of API requests to run. Each request runs in sequence, and the responses are returned in the order they've been received.
Optionally, the `require-all-validate` validation mode can be used to first validate each request's parameters and only proceed with processing if each request validates successfully.
By default, the batch size is limited to 25 requests. This can be controlled using the `rest_get_max_batch_size` filter. Clients are strongly encouraged to discover the maximum batch size supported by the server by making an OPTIONS request to the `batch/v1` endpoint and inspecting the described arguments.
Additionally, the two new methods, `match_request_to_handler` and `respond_to_request` introduced in [48947] now have a `protected` visibility as we don't want to expose the inner workings of the `WP_REST_Server::dispatch` API.
Batching is not currently supported for GET requests.
Fixes#50244.
Props andraganescu, zieladam, TimothyBlynJacobs.
git-svn-id: https://develop.svn.wordpress.org/trunk@49252 602fd350-edb4-49c9-b593-d223f7449a82
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