Alerting: Don't encrypt username for webhook notifier (#26170)

Can be hard for users to understand what user is configured
when encrypting the username field why this reverts to
store the username in cleartext.
Also, we don't encrypt username for data sources.

Ref #25967

pkg/services/alerting/notifiers/webhook.go

@@ -29,19 +29,8 @@ func init() {
 				</div>
 			</div>
 			<div class="gf-form max-width-30">
-				<div class="gf-form gf-form--v-stretch"><label class="gf-form-label width-8">Username</label></div>
-				<div class="gf-form gf-form--grow" ng-if="!ctrl.model.secureFields.username">
-					<input type="text"
-						class="gf-form-input max-width-30"
-						ng-init="ctrl.model.secureSettings.username = ctrl.model.settings.username || null; ctrl.model.settings.username = null;"
-						ng-model="ctrl.model.secureSettings.username"
-						data-placement="right">
-					</input>
-				</div>
-				<div class="gf-form" ng-if="ctrl.model.secureFields.username">
-					<input type="text" class="gf-form-input max-width-18" disabled="disabled" value="configured" />
-					<a class="btn btn-secondary gf-form-btn" href="#" ng-click="ctrl.model.secureFields.username = false">reset</a>
-				</div>
+				<span class="gf-form-label width-8">Username</span>
+				<input type="text" class="gf-form-input max-width-30" ng-model="ctrl.model.settings.username"></input>
 			</div>
 			<div class="gf-form max-width-30">
 				<div class="gf-form gf-form--v-stretch"><label class="gf-form-label width-8">Password</label></div>
@@ -106,13 +95,12 @@ func NewWebHookNotifier(model *models.AlertNotification) (alerting.Notifier, err
 		return nil, alerting.ValidationError{Reason: "Could not find url property in settings"}
 	}
 
-	username := model.DecryptedValue("username", model.Settings.Get("username").MustString())
 	password := model.DecryptedValue("password", model.Settings.Get("password").MustString())
 
 	return &WebhookNotifier{
 		NotifierBase: NewNotifierBase(model),
 		URL:          url,
-		User:         username,
+		User:         model.Settings.Get("username").MustString(),
 		Password:     password,
 		HTTPMethod:   model.Settings.Get("httpMethod").MustString("POST"),
 		log:          log.New("alerting.notifier.webhook"),