Add documentation example for receiver package (open-telemetry#5675) (open-telemetry#12922)

#### Description

This PR introduces a testable example to the package
[receiver](/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/47454f60-25d8-411b-a78f-c3e855dfd04f)


#### Documentation

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

---------

Co-authored-by: Pablo Baeyens <[email protected]>

Author: heitorganzeli

receiver/example_test.go

@@ -0,0 +1,135 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package receiver_test
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/consumer"
+	"go.opentelemetry.io/collector/pdata/pcommon"
+	"go.opentelemetry.io/collector/pdata/ptrace"
+	"go.opentelemetry.io/collector/receiver"
+)
+
+var typeStr = component.MustNewType("example")
+
+type exampleConfig struct {
+	Interval time.Duration
+}
+
+// Reciver must implement the Start() and Shutdown() methods so the receiver type can be compliant
+// with the receiver.Traces interface.
+type exampleReceiver struct {
+	host         component.Host
+	cancel       context.CancelFunc
+	nextConsumer consumer.Traces
+	config       exampleConfig
+}
+
+func (rcvr *exampleReceiver) Start(ctx context.Context, host component.Host) error {
+	rcvr.host = host
+	ctx, rcvr.cancel = context.WithCancel(ctx)
+
+	go func() {
+		ticker := time.NewTicker(rcvr.config.Interval)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-ticker.C:
+				// Your receiver processing code should come here
+				err := rcvr.nextConsumer.ConsumeTraces(ctx, generateTrace())
+				if err != nil {
+					fmt.Println("Error when consuming trace: %w", err)
+				}
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	return nil
+}
+
+func (rcvr *exampleReceiver) Shutdown(_ context.Context) error {
+	if rcvr.cancel != nil {
+		rcvr.cancel()
+	}
+	return nil
+}
+
+func generateTrace() ptrace.Traces {
+	traces := ptrace.NewTraces()
+
+	// In reallity you may need to fetch or receive and transform
+	// some telemetry data.
+	// For this example we will just generate some dummy data
+	resourceSpan := traces.ResourceSpans().AppendEmpty()
+	resource := resourceSpan.Resource()
+
+	attrs := resource.Attributes()
+	attrs.PutInt("id", 1)
+
+	scopeSpans := resourceSpan.ScopeSpans().AppendEmpty()
+	scopeSpans.Scope().SetName("example-system")
+	scopeSpans.Scope().SetVersion("v1.0")
+
+	traceID := pcommon.TraceID([]byte("1"))
+	spanID := pcommon.SpanID([]byte("2"))
+
+	span := scopeSpans.Spans().AppendEmpty()
+	span.SetTraceID(traceID)
+	span.SetSpanID(spanID)
+	span.SetName("Operation 1")
+	span.SetKind(ptrace.SpanKindClient)
+	span.Status().SetCode(ptrace.StatusCodeOk)
+	span.SetStartTimestamp(pcommon.NewTimestampFromTime(time.Now()))
+	span.SetEndTimestamp(pcommon.NewTimestampFromTime(time.Now().Add(4 * time.Millisecond)))
+
+	// Other resources and spans could also be added.
+
+	return traces
+}
+
+func createDefaultConfig() component.Config {
+	return &exampleConfig{
+		Interval: time.Minute,
+	}
+}
+
+func createExampleReceiver(_ context.Context, _ receiver.Settings,
+	baseCfg component.Config, consumer consumer.Traces,
+) (receiver.Traces, error) {
+	exampleCfg := baseCfg.(*exampleConfig)
+
+	rcvr := &exampleReceiver{
+		nextConsumer: consumer,
+		config:       *exampleCfg,
+	}
+
+	return rcvr, nil
+}
+
+func NewFactory() receiver.Factory {
+	return receiver.NewFactory(
+		typeStr,
+		createDefaultConfig,
+		receiver.WithTraces(createExampleReceiver, component.StabilityLevelAlpha))
+}
+
+func Example() {
+	// The NewFactory method can then be used on the Collector's initialization process
+	// on your components.go file.
+
+	// In this example we will just instantiate and print it's type
+
+	exampleReceiver := NewFactory()
+	fmt.Println(exampleReceiver.Type())
+
+	// Output:
+	// example
+}

receiver/go.mod

@@ -7,6 +7,7 @@ require (
 	go.opentelemetry.io/collector/component v1.31.0
 	go.opentelemetry.io/collector/consumer v1.31.0
 	go.opentelemetry.io/collector/consumer/consumertest v0.125.0
+	go.opentelemetry.io/collector/pdata v1.31.0
 	go.opentelemetry.io/collector/pipeline v0.125.0
 	go.uber.org/goleak v1.3.0
 )
@@ -26,7 +27,6 @@ require (
 	go.opentelemetry.io/collector/consumer/xconsumer v0.125.0 // indirect
 	go.opentelemetry.io/collector/featuregate v1.31.0 // indirect
 	go.opentelemetry.io/collector/internal/telemetry v0.125.0 // indirect
-	go.opentelemetry.io/collector/pdata v1.31.0 // indirect
 	go.opentelemetry.io/collector/pdata/pprofile v0.125.0 // indirect
 	go.opentelemetry.io/contrib/bridges/otelzap v0.10.0 // indirect
 	go.opentelemetry.io/otel v1.35.0 // indirect