feat: support for url based icons (#840)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/utils/file_util.go

@@ -7,6 +7,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"mime"
 	"mime/multipart"
 	"os"
 	"path/filepath"
@@ -57,6 +58,34 @@ func GetImageMimeType(ext string) string {
 	}
 }
 
+func GetImageExtensionFromMimeType(mimeType string) string {
+	// Normalize and strip parameters like `; charset=utf-8`
+	mt := strings.TrimSpace(strings.ToLower(mimeType))
+	if v, _, err := mime.ParseMediaType(mt); err == nil {
+		mt = v
+	}
+	switch mt {
+	case "image/jpeg", "image/jpg":
+		return "jpg"
+	case "image/png":
+		return "png"
+	case "image/svg+xml":
+		return "svg"
+	case "image/x-icon", "image/vnd.microsoft.icon":
+		return "ico"
+	case "image/gif":
+		return "gif"
+	case "image/webp":
+		return "webp"
+	case "image/avif":
+		return "avif"
+	case "image/heic", "image/heif":
+		return "heic"
+	default:
+		return ""
+	}
+}
+
 func CopyEmbeddedFileToDisk(srcFilePath, destFilePath string) error {
 	srcFile, err := resources.FS.Open(srcFilePath)
 	if err != nil {