{{define "header"}}<div class="email-header">
  {{- if .LogoURL}}
  <a href="{{.AppURL}}"><img src="{{.LogoURL}}" alt="{{.AppName}}" class="app-logo"></a>
  {{- else}}
  <a href="{{.AppURL}}" class="app-name">{{.AppName}}</a>
  {{- end}}
</div>
{{end}}