refac: repository updates, image attachment and deletes report the domain not-found error for an unknown id, the same for articles, users and images, and the test fakes stop returning GORM errors

internal/domain/image/imageDomain.go

@@ -1,10 +1,13 @@
 package image
 
 import (
+	"errors"
 	"io"
 	"time"
 )
 
+var ErrImageNotFound = errors.New("image not found")
+
 type ImageInput struct {
 	Content     io.Reader
 	Filename    string