feat(api/gateway): add DirectResponse CRD for static HTTP responses

Add a new Gateway API extension CRD called DirectResponse that allows HTTPRoute
rules to return static HTTP responses without a backend service. This supports
the HTTP-01 ACME challenge workflow for serving challenge tokens directly from
Envoy.

Changes:
- Create api/gateway/v1alpha1/ package with DirectResponse type definition
- Implement DirectResponseSpec with status code, content-type, headers, and body
- Generate deepcopy and register helpers via k8s.io/code-generator
- Update codegen/update.sh to include v1alpha1 in code generation pipeline
- Generate versioned client code for gateway.apoxy.dev/v1alpha1

Author: theRealWardo

api/extensions/v1alpha2/directresponse_types.go

@@ -0,0 +1,98 @@
+package v1alpha2
+
+import (
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+// BodyType defines how the response body is specified.
+// +kubebuilder:validation:Enum=Inline
+type BodyType string
+
+const (
+	// BodyTypeInline indicates the body is specified inline as a string.
+	BodyTypeInline BodyType = "Inline"
+)
+
+// CustomResponseBody defines the body of the direct response.
+type CustomResponseBody struct {
+	// Type specifies how the body is provided.
+	// Currently only "Inline" is supported.
+	// +kubebuilder:validation:Required
+	Type BodyType `json:"type"`
+
+	// Inline is the literal body content when Type is "Inline".
+	// +optional
+	Inline *string `json:"inline,omitempty"`
+}
+
+// Header defines a custom HTTP header to include in the response.
+type Header struct {
+	// Name is the header name.
+	// +kubebuilder:validation:Required
+	// +kubebuilder:validation:MinLength=1
+	Name string `json:"name"`
+
+	// Value is the header value.
+	// +kubebuilder:validation:Required
+	Value string `json:"value"`
+}
+
+// DirectResponseSpec defines the desired state of DirectResponse.
+type DirectResponseSpec struct {
+	// StatusCode is the HTTP status code to return.
+	// Defaults to 200 if not specified.
+	// +kubebuilder:validation:Minimum=100
+	// +kubebuilder:validation:Maximum=599
+	// +kubebuilder:default=200
+	// +optional
+	StatusCode *int32 `json:"statusCode,omitempty"`
+
+	// ContentType is the Content-Type header value.
+	// Defaults to "text/plain" if not specified.
+	// +kubebuilder:default="text/plain"
+	// +optional
+	ContentType *string `json:"contentType,omitempty"`
+
+	// Headers are additional HTTP headers to include in the response.
+	// +optional
+	Headers []Header `json:"headers,omitempty"`
+
+	// Body is the response body configuration.
+	// +optional
+	Body *CustomResponseBody `json:"body,omitempty"`
+}
+
+// DirectResponseStatus defines the observed state of DirectResponse.
+type DirectResponseStatus struct {
+	// Conditions describe the current conditions of the DirectResponse.
+	// +optional
+	Conditions []metav1.Condition `json:"conditions,omitempty"`
+}
+
+// +kubebuilder:object:root=true
+// +kubebuilder:subresource:status
+// +kubebuilder:resource:categories=gateway-api
+// +kubebuilder:printcolumn:name="Status Code",type=integer,JSONPath=`.spec.statusCode`
+// +kubebuilder:printcolumn:name="Age",type=date,JSONPath=`.metadata.creationTimestamp`
+// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
+
+// DirectResponse is the Schema for the directresponses API.
+// It defines a static response that can be returned by an HTTPRoute
+// instead of forwarding to a backend.
+type DirectResponse struct {
+	metav1.TypeMeta   `json:",inline"`
+	metav1.ObjectMeta `json:"metadata,omitempty"`
+
+	Spec   DirectResponseSpec   `json:"spec,omitempty"`
+	Status DirectResponseStatus `json:"status,omitempty"`
+}
+
+// +kubebuilder:object:root=true
+// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
+
+// DirectResponseList contains a list of DirectResponse.
+type DirectResponseList struct {
+	metav1.TypeMeta `json:",inline"`
+	metav1.ListMeta `json:"metadata,omitempty"`
+	Items           []DirectResponse `json:"items"`
+}