chore: use partial includes in mail templates to avoid code duplication

utils/template.go

@@ -3,8 +3,13 @@ package utils
 import (
 	"encoding/json"
 	"html/template"
+	"io/fs"
+	"io/ioutil"
+	"path"
 )
 
+type TemplateMap map[string]*template.Template
+
 func Json(data interface{}) template.JS {
 	d, err := json.Marshal(data)
 	if err != nil {
@@ -19,3 +24,40 @@ func ToRunes(s string) (r []string) {
 	}
 	return r
 }
+
+func LoadTemplates(templateFs fs.FS, funcs template.FuncMap) (TemplateMap, error) {
+	tpls := template.New("").Funcs(funcs)
+	templates := make(map[string]*template.Template)
+
+	files, err := fs.ReadDir(templateFs, ".")
+	if err != nil {
+		return nil, err
+	}
+
+	for _, file := range files {
+		tplName := file.Name()
+		if file.IsDir() || path.Ext(tplName) != ".html" {
+			continue
+		}
+
+		templateFile, err := templateFs.Open(tplName)
+		if err != nil {
+			return nil, err
+		}
+		templateData, err := ioutil.ReadAll(templateFile)
+		if err != nil {
+			return nil, err
+		}
+
+		templateFile.Close()
+
+		tpl, err := tpls.New(tplName).Parse(string(templateData))
+		if err != nil {
+			return nil, err
+		}
+
+		templates[tplName] = tpl
+	}
+
+	return templates, nil
+}