[exporter/otlphttpexporter] Use NewDefaultClientConfig instead of manually creating struct

This PR makes usage of `NewDefaultClientConfig` instead of manually creating the confighttp.ClientConfig struct. The updates to defaults are maintained (Timeout, Compression, WriteBufferSize) whereas the fields that match the default are not manually set anymore (Endpoint, Headers).

Issue: open-telemetry#9478 (comment)

Author: mackjmr

exporter/otlphttpexporter/factory.go

@@ -13,7 +13,6 @@ import (
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/config/configcompression"
 	"go.opentelemetry.io/collector/config/confighttp"
-	"go.opentelemetry.io/collector/config/configopaque"
 	"go.opentelemetry.io/collector/config/configretry"
 	"go.opentelemetry.io/collector/consumer"
 	"go.opentelemetry.io/collector/exporter"
@@ -33,19 +32,18 @@ func NewFactory() exporter.Factory {
 }
 
 func createDefaultConfig() component.Config {
+	clientConfig := confighttp.NewDefaultClientConfig()
+	clientConfig.Timeout = 30 * time.Second
+	// Default to gzip compression
+	clientConfig.Compression = configcompression.TypeGzip
+	// We almost read 0 bytes, so no need to tune ReadBufferSize.
+	clientConfig.WriteBufferSize = 512 * 1024
+
 	return &Config{
-		RetryConfig: configretry.NewDefaultBackOffConfig(),
-		QueueConfig: exporterhelper.NewDefaultQueueConfig(),
-		Encoding:    EncodingProto,
-		ClientConfig: confighttp.ClientConfig{
-			Endpoint: "",
-			Timeout:  30 * time.Second,
-			Headers:  map[string]configopaque.String{},
-			// Default to gzip compression
-			Compression: configcompression.TypeGzip,
-			// We almost read 0 bytes, so no need to tune ReadBufferSize.
-			WriteBufferSize: 512 * 1024,
-		},
+		RetryConfig:  configretry.NewDefaultBackOffConfig(),
+		QueueConfig:  exporterhelper.NewDefaultQueueConfig(),
+		Encoding:     EncodingProto,
+		ClientConfig: clientConfig,
 	}
 }