chore: use gotemplate for invitation email

auth/controllers.go

@@ -1,6 +1,7 @@
 package auth
 
 import (
+	"bytes"
 	"fmt"
 	"net/http"
 	"os"
@@ -69,19 +70,27 @@ func (k *KratosHandler) InviteUser(c echo.Context) error {
 		return c.JSON(http.StatusInternalServerError, dutyAPI.HTTPError{Err: err.Error(), Message: "error creating recovery link"})
 	}
 
-	body := fmt.Sprintf(inviteUserTemplate, reqData.FirstName, recoveryLink, recoveryCode)
-	inviteMail := mail.New(reqData.Email, "User Invite", body, "text/html")
+	data := map[string]string{
+		"firstName": reqData.FirstName,
+		"link":      recoveryLink,
+		"code":      recoveryCode,
+	}
+
+	var body bytes.Buffer
+	if err := inviteUserTemplate.Execute(&body, data); err != nil {
+		return err
+	}
+
+	inviteMail := mail.New(reqData.Email, "User Invite", body.String(), "text/html")
 	if err = inviteMail.Send(); err != nil {
 		return c.JSON(http.StatusInternalServerError, dutyAPI.HTTPError{
 			Err:     err.Error(),
 			Message: "Error sending email",
 		})
 	}
 
-	return c.JSON(http.StatusOK, map[string]string{
-		"link": recoveryLink,
-		"code": recoveryCode,
-	})
+	delete(data, "firstName")
+	return c.JSON(http.StatusOK, data)
 }
 
 func UpdateAccountState(c echo.Context) error {

auth/templates.go

@@ -1,8 +1,23 @@
 package auth
 
-const inviteUserTemplate = `
+import (
+	"fmt"
+	"html/template"
+
+	"github.com/flanksource/duty/shutdown"
+)
+
+var inviteUserTemplate *template.Template
+
+func init() {
+	parsed, err := template.New("email").Parse(`
 <b>Welcome to Mission Control</b>
 <br><br>
-Hello %s,
+Hello {{.firstName}},<br>
+Please visit <a href="{{.link}}">{{.link}}</a> to complete registration and use the code: <code>{{.code}}</code>`)
+	if err != nil {
+		shutdown.ShutdownAndExit(1, fmt.Sprintf("failed to parse invitation email template: %v", err))
+	}
 
-please visit <a href="%s">this link</a> to complete registration and use the code: <code>%s</code>`
+	inviteUserTemplate = parsed
+}