log: Add EventName (#6187)

Fixes https://github.com/open-telemetry/opentelemetry-go/issues/6182
Towards https://github.com/open-telemetry/opentelemetry-go/issues/6184

Towards https://github.com/open-telemetry/opentelemetry-go/issues/6181

Prior-art: https://github.com/open-telemetry/opentelemetry-go/pull/6018

log/logtest/assertions.go

@@ -15,6 +15,10 @@ import (
 func AssertRecordEqual(t testing.TB, want, got log.Record) bool {
 	t.Helper()
 
+	if want.EventName() != got.EventName() {
+		t.Errorf("EventName value is not equal:\nwant: %v\ngot:  %v", want.EventName(), got.EventName())
+		return false
+	}
 	if !want.Timestamp().Equal(got.Timestamp()) {
 		t.Errorf("Timestamp value is not equal:\nwant: %v\ngot:  %v", want.Timestamp(), got.Timestamp())
 		return false

log/logtest/assertions_test.go

@@ -13,10 +13,11 @@ import (
 func TestAssertRecord(t *testing.T) {
 	r1 := log.Record{}
 	r2 := log.Record{}
-	now := time.Now()
-
 	AssertRecordEqual(t, r1, r2)
 
+	now := time.Now()
+	r1.SetEventName("my_event")
+	r2.SetEventName("my_event")
 	r1.SetTimestamp(now)
 	r2.SetTimestamp(now)
 	r1.SetObservedTimestamp(now)

log/logtest/factory.go

@@ -14,6 +14,7 @@ import (
 //
 // Do not use RecordFactory to create records in production code.
 type RecordFactory struct {
+	EventName         string
 	Timestamp         time.Time
 	ObservedTimestamp time.Time
 	Severity          log.Severity
@@ -25,6 +26,7 @@ type RecordFactory struct {
 // NewRecord returns a log record.
 func (b RecordFactory) NewRecord() log.Record {
 	var record log.Record
+	record.SetEventName(b.EventName)
 	record.SetTimestamp(b.Timestamp)
 	record.SetObservedTimestamp(b.ObservedTimestamp)
 	record.SetSeverity(b.Severity)

log/logtest/factory_test.go

@@ -15,6 +15,7 @@ import (
 func TestRecordFactory(t *testing.T) {
 	now := time.Now()
 	observed := now.Add(time.Second)
+	evnt := "my_event"
 	severity := log.SeverityDebug
 	severityText := "DBG"
 	body := log.StringValue("Message")
@@ -25,6 +26,7 @@ func TestRecordFactory(t *testing.T) {
 	}
 
 	got := RecordFactory{
+		EventName:         evnt,
 		Timestamp:         now,
 		ObservedTimestamp: observed,
 		Severity:          severity,
@@ -33,6 +35,7 @@ func TestRecordFactory(t *testing.T) {
 		Attributes:        attrs,
 	}.NewRecord()
 
+	assert.Equal(t, evnt, got.EventName())
 	assert.Equal(t, now, got.Timestamp())
 	assert.Equal(t, observed, got.ObservedTimestamp())
 	assert.Equal(t, severity, got.Severity())