[#219] Use zaptest.Logger

Use zaptest to get logs which get printed only if a test fails
or if you ran go test -v.

Dont use zaptest.Logger for fuzz otherwise ngfuzz/libfuzz crashes

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

internal/handler/multipart_test.go

@@ -60,12 +60,7 @@ func BenchmarkAll(b *testing.B) {
 func defaultMultipart(filename string) error {
 	r, bound := multipartFile(filename)
 
-	logger, err := zap.NewProduction()
-	if err != nil {
-		return err
-	}
-
-	file, err := fetchMultipartFileDefault(logger, r, bound)
+	file, err := fetchMultipartFileDefault(zap.NewNop(), r, bound)
 	if err != nil {
 		return err
 	}
@@ -87,12 +82,7 @@ func TestName(t *testing.T) {
 func customMultipart(filename string) error {
 	r, bound := multipartFile(filename)
 
-	logger, err := zap.NewProduction()
-	if err != nil {
-		return err
-	}
-
-	file, err := fetchMultipartFile(logger, r, bound)
+	file, err := fetchMultipartFile(zap.NewNop(), r, bound)
 	if err != nil {
 		return err
 	}