[chore] follow the contract of createDefaultConfig (#40541)

This will help when we scan for the Config struct with checkapi.

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: atoulme

receiver/kafkareceiver/factory.go

@@ -29,16 +29,14 @@ const (
 func NewFactory() receiver.Factory {
 	return receiver.NewFactory(
 		metadata.Type,
-		func() component.Config {
-			return createDefaultConfig()
-		},
+		createDefaultConfig,
 		receiver.WithTraces(createTracesReceiver, metadata.TracesStability),
 		receiver.WithMetrics(createMetricsReceiver, metadata.MetricsStability),
 		receiver.WithLogs(createLogsReceiver, metadata.LogsStability),
 	)
 }
 
-func createDefaultConfig() *Config {
+func createDefaultConfig() component.Config {
 	return &Config{
 		ClientConfig:   configkafka.NewDefaultClientConfig(),
 		ConsumerConfig: configkafka.NewDefaultConsumerConfig(),

receiver/kafkareceiver/factory_test.go

@@ -17,15 +17,15 @@ import (
 )
 
 func TestCreateDefaultConfig(t *testing.T) {
-	cfg := createDefaultConfig()
+	cfg := createDefaultConfig().(*Config)
 	assert.NotNil(t, cfg, "failed to create default config")
 	assert.NoError(t, componenttest.CheckConfigStruct(cfg))
 	assert.Equal(t, configkafka.NewDefaultClientConfig(), cfg.ClientConfig)
 	assert.Equal(t, configkafka.NewDefaultConsumerConfig(), cfg.ConsumerConfig)
 }
 
 func TestCreateTraces(t *testing.T) {
-	cfg := createDefaultConfig()
+	cfg := createDefaultConfig().(*Config)
 	cfg.Brokers = []string{"invalid:9092"}
 	cfg.ProtocolVersion = "2.0.0"
 	r, err := createTracesReceiver(context.Background(), receivertest.NewNopSettings(metadata.Type), cfg, nil)
@@ -38,7 +38,7 @@ func TestWithTracesUnmarshalers(t *testing.T) {
 	f := NewFactory()
 
 	t.Run("custom_encoding", func(t *testing.T) {
-		cfg := createDefaultConfig()
+		cfg := createDefaultConfig().(*Config)
 		cfg.Traces.Encoding = "custom"
 		receiver, err := f.CreateTraces(context.Background(), receivertest.NewNopSettings(metadata.Type), cfg, nil)
 		tracesConsumer, ok := receiver.(*kafkaConsumer)
@@ -59,7 +59,7 @@ func TestWithTracesUnmarshalers(t *testing.T) {
 }
 
 func TestCreateMetrics(t *testing.T) {
-	cfg := createDefaultConfig()
+	cfg := createDefaultConfig().(*Config)
 	cfg.Brokers = []string{"invalid:9092"}
 	cfg.ProtocolVersion = "2.0.0"
 	r, err := createMetricsReceiver(context.Background(), receivertest.NewNopSettings(metadata.Type), cfg, nil)
@@ -72,7 +72,7 @@ func TestWithMetricsUnmarshalers(t *testing.T) {
 	f := NewFactory()
 
 	t.Run("custom_encoding", func(t *testing.T) {
-		cfg := createDefaultConfig()
+		cfg := createDefaultConfig().(*Config)
 		cfg.Metrics.Encoding = "custom"
 		receiver, err := f.CreateMetrics(context.Background(), receivertest.NewNopSettings(metadata.Type), cfg, nil)
 		metricsConsumer, ok := receiver.(*kafkaConsumer)
@@ -93,7 +93,7 @@ func TestWithMetricsUnmarshalers(t *testing.T) {
 }
 
 func TestCreateLogs(t *testing.T) {
-	cfg := createDefaultConfig()
+	cfg := createDefaultConfig().(*Config)
 	cfg.Brokers = []string{"invalid:9092"}
 	cfg.ProtocolVersion = "2.0.0"
 	r, err := createLogsReceiver(context.Background(), receivertest.NewNopSettings(metadata.Type), cfg, nil)
@@ -106,7 +106,7 @@ func TestWithLogsUnmarshalers(t *testing.T) {
 	f := NewFactory()
 
 	t.Run("custom_encoding", func(t *testing.T) {
-		cfg := createDefaultConfig()
+		cfg := createDefaultConfig().(*Config)
 		cfg.Logs.Encoding = "custom"
 		receiver, err := f.CreateLogs(context.Background(), receivertest.NewNopSettings(metadata.Type), cfg, nil)
 		logsConsumer, ok := receiver.(*kafkaConsumer)

receiver/kafkareceiver/kafka_receiver_test.go

@@ -597,7 +597,7 @@ func mustNewFakeCluster(tb testing.TB, opts ...kfake.Opt) (*kgo.Client, *Config)
 	kafkaClient := mustNewClient(tb, cluster)
 	tb.Cleanup(func() { deleteConsumerGroups(tb, kafkaClient) })
 
-	cfg := createDefaultConfig()
+	cfg := createDefaultConfig().(*Config)
 	cfg.ClientConfig = clientConfig
 	cfg.InitialOffset = "earliest"
 	cfg.MaxFetchWait = time.Millisecond