[configauth] Add omitempty tags to fields (#12481)

<!-- Issue number if applicable -->
#### Link to tracking issue

Works toward
#12191

Author: evan-bradley

.chloggen/configauth-omitempty.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: configauth
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add the `omitempty` mapstructure tag to struct fields
+
+# One or more tracking issues or pull requests related to the change
+issues: [12191]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: This results in unset fields not being rendered when marshaling.
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

config/configauth/configauth.go

@@ -24,7 +24,7 @@ var (
 // Authentication defines the auth settings for the receiver.
 type Authentication struct {
 	// AuthenticatorID specifies the name of the extension to use in order to authenticate the incoming data point.
-	AuthenticatorID component.ID `mapstructure:"authenticator"`
+	AuthenticatorID component.ID `mapstructure:"authenticator,omitempty"`
 }
 
 // GetServerAuthenticator attempts to select the appropriate extensionauth.Server from the list of extensions,

internal/e2e/configauth_test.go

@@ -0,0 +1,20 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package e2e
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/config/configauth"
+	"go.opentelemetry.io/collector/confmap"
+)
+
+func TestConfmapMarshalConfigAuth(t *testing.T) {
+	conf := confmap.New()
+	require.NoError(t, conf.Marshal(configauth.Authentication{}))
+	assert.Equal(t, map[string]any{}, conf.ToStringMap())
+}

internal/e2e/go.mod

@@ -8,6 +8,7 @@ require (
 	go.opentelemetry.io/collector/component v0.120.0
 	go.opentelemetry.io/collector/component/componentstatus v0.120.0
 	go.opentelemetry.io/collector/component/componenttest v0.120.0
+	go.opentelemetry.io/collector/config/configauth v0.120.0
 	go.opentelemetry.io/collector/config/configgrpc v0.120.0
 	go.opentelemetry.io/collector/config/confighttp v0.120.0
 	go.opentelemetry.io/collector/config/confignet v1.26.0
@@ -80,7 +81,6 @@ require (
 	github.com/yusufpapurcu/wmi v1.2.4 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/collector/client v1.26.0 // indirect
-	go.opentelemetry.io/collector/config/configauth v0.120.0 // indirect
 	go.opentelemetry.io/collector/config/configcompression v1.26.0 // indirect
 	go.opentelemetry.io/collector/connector/xconnector v0.120.0 // indirect
 	go.opentelemetry.io/collector/consumer/consumererror v0.120.0 // indirect