Allow to disable exiftool if env variable is set

This allows more flexible way to enable/disable exiftool

changelogs/unreleased/exif-var.yml

+---
+title: Allow to disable exiftool depending on env variable.
+merge_request:
+author:
+type: security

workhorse/internal/upload/exif/exif.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"os"
 	"os/exec"
 	"regexp"
 
@@ -101,6 +102,9 @@ func (c *cleaner) startProcessing(stdin io.Reader) error {
 }
 
 func IsExifFile(filename string) bool {
+	if os.Getenv("SKIP_EXIFTOOL") == "1" {
+		return false
+	}
 	filenameMatch := regexp.MustCompile(`(?i)\.(jpg|jpeg|tiff)$`)
 
 	return filenameMatch.MatchString(filename)