feat(flowcontrol): Add bundled Flow Control config

Introduces a new top-level `Config` for the Flow Control layer.

This config bundles the configurations for the `controller` and
`registry` packages, providing a single, unified point of entry fo
validation and default application. This simplifies the management and
initialization of the flow control system by centralizing its
configuration.

Author: LukeAVanDrie

pkg/epp/flowcontrol/config.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package flowcontrol
+
+import (
+	"fmt"
+
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/controller"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/registry"
+)
+
+// Config is the top-level configuration for the entire flow control module.
+// It embeds the configurations for the controller and the registry, providing a single point of entry for validation
+// and initialization.
+type Config struct {
+	Controller controller.Config
+	Registry   registry.Config
+}
+
+// ValidateAndApplyDefaults checks the configuration for validity and populates any empty fields with system defaults.
+// It delegates validation to the underlying controller and registry configurations.
+// It returns a new, validated `Config` object and does not mutate the receiver.
+func (c *Config) ValidateAndApplyDefaults() (*Config, error) {
+	validatedControllerCfg, err := c.Controller.ValidateAndApplyDefaults()
+	if err != nil {
+		return nil, fmt.Errorf("controller config validation failed: %w", err)
+	}
+	validatedRegistryCfg, err := c.Registry.ValidateAndApplyDefaults()
+	if err != nil {
+		return nil, fmt.Errorf("registry config validation failed: %w", err)
+	}
+	return &Config{
+		Controller: *validatedControllerCfg,
+		Registry:   *validatedRegistryCfg,
+	}, nil
+}

pkg/epp/flowcontrol/config_test.go

@@ -0,0 +1,91 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package flowcontrol
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/controller"
+	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/registry"
+)
+
+func TestConfig_ValidateAndApplyDefaults(t *testing.T) {
+	t.Parallel()
+
+	// A minimal valid registry config, which is required for the success case.
+	validRegistryConfig := registry.Config{
+		PriorityBands: []registry.PriorityBandConfig{
+			{Priority: 1, PriorityName: "TestBand"},
+		},
+	}
+
+	testCases := []struct {
+		name          string
+		input         Config
+		expectErr     bool
+		expectedErrIs error
+	}{
+		{
+			name: "ShouldSucceed_WhenSubConfigsAreValid",
+			input: Config{
+				Controller: controller.Config{},
+				Registry:   validRegistryConfig,
+			},
+			expectErr: false,
+		},
+		{
+			name: "ShouldFail_WhenControllerConfigIsInvalid",
+			input: Config{
+				Controller: controller.Config{
+					DefaultRequestTTL: -1 * time.Second,
+				},
+				Registry: validRegistryConfig,
+			},
+			expectErr: true,
+		},
+		{
+			name: "ShouldFail_WhenRegistryConfigIsInvalid",
+			input: Config{
+				Controller: controller.Config{},
+				Registry: registry.Config{
+					PriorityBands: []registry.PriorityBandConfig{},
+				},
+			},
+			expectErr: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			originalInput := tc.input
+			validatedCfg, err := tc.input.ValidateAndApplyDefaults()
+
+			if tc.expectErr {
+				require.Error(t, err, "expected an error but got nil")
+			} else {
+				require.NoError(t, err, "expected no error but got: %v", err)
+				require.NotNil(t, validatedCfg, "validatedCfg should not be nil on success")
+			}
+
+			assert.Equal(t, originalInput, tc.input, "input config should not be mutated")
+		})
+	}
+}