feat(email): improve email templating (#27)

backend/internal/service/email_service_templates.go

@@ -0,0 +1,37 @@
+package service
+
+import (
+	"fmt"
+	"github.com/stonith404/pocket-id/backend/internal/utils/email"
+	"time"
+)
+
+/**
+How to add new template:
+- pick unique and descriptive template ${name} (for example "login-with-new-device")
+- in backend/email-templates/ create "${name}_html.tmpl" and "${name}_text.tmpl"
+- create xxxxTemplate and xxxxTemplateData (for example NewLoginTemplate and NewLoginTemplateData)
+  - Path *must* be ${name}
+- add xxxTemplate.Path to "emailTemplatePaths" at the end
+
+Notes:
+- backend app must be restarted to reread all the template files
+- root "." object in templates is `email.TemplateData`
+- xxxxTemplateData structure is visible under .Data in templates
+*/
+
+var NewLoginTemplate = email.Template[NewLoginTemplateData]{
+	Path: "login-with-new-device",
+	Title: func(data *email.TemplateData[NewLoginTemplateData]) string {
+		return fmt.Sprintf("New device login with %s", data.AppName)
+	},
+}
+
+type NewLoginTemplateData struct {
+	IPAddress string
+	Device    string
+	DateTime  time.Time
+}
+
+// this is list of all template paths used for preloading templates
+var emailTemplatesPaths = []string{NewLoginTemplate.Path}