Pruning is activated by setting `spec.preserveUnknownFields: false` in the CustomResourceDefinition. A future apiextensions.k8s.io/v1 variant of CRDs will enforce pruning.

Pruning requires that CRD developer provides complete, structural validation schemas, either at the top-level or for all versions of the CRD.

#### CustomResourceDefinition Defaulting

  repeated HTTPHeader httpHeaders = 5;
}

// HTTPHeader describes a custom header to be used in HTTP probes
message HTTPHeader {
  // The header field name.
  // This will be canonicalized upon output, so case-variant names will be understood as the same header.
  optional string name = 1;

  // The header field value
  optional string value = 2;
}

by automatic tools such as integrated development environments.
</p>

<h2 id="Notation">Notation</h2>
<p>
The syntax is specified using a
<a href="https://en.wikipedia.org/wiki/Wirth_syntax_notation">variant</a>
of Extended Backus-Naur Form (EBNF):
</p>

<pre class="grammar">
Syntax      = { Production } .
Production  = production_name "=" [ Expression ] "." .
Expression  = Term { "|" Term } .

        "properties": {
          "name": {
            "default": "",
            "description": "The header field name. This will be canonicalized upon output, so case-variant names will be understood as the same header.",
            "type": "string"
          },
          "value": {
            "default": "",
            "description": "The header field value",