Add documentation example for exporter package (open-telemetry#5675) (open-telemetry#12958)

#### Description

This PR introduces a testable example to the package
[exporter](/receiver). it's a similar example to the documentation one
on
https://opentelemetry.io/docs/collector/building/receiver/#designing-and-validating-receiver-settings

#### Issue:
open-telemetry#5675 (comment)

#### Testing

the testable example was executed successfully


![image](https://github.com/user-attachments/assets/0843a710-767b-4746-81d3-81fe05dec472)

#### Documentation

this testable example follows
https://go.dev/blog/examples#larger-examples format and should be
automatically added to `exporter` package documentation

Co-authored-by: Damien Mathieu <[email protected]>

Author: heitorganzeli

exporter/example_test.go

@@ -0,0 +1,114 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package exporter_test
+
+import (
+	"context"
+	"fmt"
+
+	"go.uber.org/zap"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/configretry"
+	"go.opentelemetry.io/collector/consumer"
+	"go.opentelemetry.io/collector/exporter"
+	"go.opentelemetry.io/collector/exporter/exporterhelper"
+	"go.opentelemetry.io/collector/pdata/pmetric"
+)
+
+// typeStr defines the unique type identifier for the exporter.
+var typeStr = component.MustNewType("example")
+
+// exampleConfig holds configuration settings for the exporter.
+type exampleConfig struct {
+	QueueSettings exporterhelper.QueueBatchConfig
+	BackOffConfig configretry.BackOffConfig
+}
+
+// exampleExporter implements the OpenTelemetry exporter interface.
+type exampleExporter struct {
+	cancel context.CancelFunc
+	config exampleConfig
+	client *loggerClient
+}
+
+// loggerClient wraps a Zap logger to provide logging functionality.
+type loggerClient struct {
+	logger *zap.Logger
+}
+
+// Example demonstrates the usage of the exporter factory.
+func Example() {
+	// Instantiate the exporter factory and print its type.
+	exampleExporter := NewFactory()
+	fmt.Println(exampleExporter.Type())
+
+	// Output:
+	// example
+}
+
+// NewFactory creates a new exporter factory.
+func NewFactory() exporter.Factory {
+	return exporter.NewFactory(
+		typeStr,
+		createDefaultConfig,
+		exporter.WithMetrics(createExampleExporter, component.StabilityLevelAlpha),
+	)
+}
+
+// createDefaultConfig returns the default configuration for the exporter.
+func createDefaultConfig() component.Config {
+	return &exampleConfig{}
+}
+
+// createExampleExporter initializes an instance of the example exporter.
+func createExampleExporter(ctx context.Context, params exporter.Settings, baseCfg component.Config) (exporter.Metrics, error) {
+	// Convert baseCfg to the correct type.
+	cfg := baseCfg.(*exampleConfig)
+
+	// Create a new exporter instance.
+	xptr := newExampleExporter(ctx, cfg, params)
+
+	// Wrap the exporter with the helper utilities.
+	return exporterhelper.NewMetrics(
+		ctx,
+		params,
+		cfg,
+		xptr.consumeMetrics,
+		exporterhelper.WithQueue(cfg.QueueSettings),
+		exporterhelper.WithRetry(cfg.BackOffConfig),
+		exporterhelper.WithCapabilities(consumer.Capabilities{MutatesData: false}),
+		exporterhelper.WithShutdown(xptr.shutdown),
+	)
+}
+
+// newExampleExporter constructs a new instance of the example exporter.
+func newExampleExporter(ctx context.Context, cfg *exampleConfig, params exporter.Settings) *exampleExporter {
+	xptr := &exampleExporter{
+		config: *cfg,
+		client: &loggerClient{logger: params.Logger},
+	}
+
+	// Create a cancelable context.
+	_, xptr.cancel = context.WithCancel(ctx)
+
+	return xptr
+}
+
+// consumeMetrics processes incoming metric data and logs it.
+func (xptr *exampleExporter) consumeMetrics(_ context.Context, md pmetric.Metrics) error {
+	xptr.client.Push(md)
+	return nil
+}
+
+// Shutdown properly stops the exporter and releases resources.
+func (xptr *exampleExporter) shutdown(_ context.Context) error {
+	xptr.cancel()
+	return nil
+}
+
+// Push logs the received metric data.
+func (client *loggerClient) Push(md pmetric.Metrics) {
+	client.logger.Info("Exporting metrics", zap.Any("metrics", md))
+}