Stage uploads before accepting HTTP runs

internal/ingest/archive.go

@@ -138,6 +138,11 @@ func validateRunID(value string) error {
 	return nil
 }
 
+func ValidateContentType(contentType string) error {
+	_, err := archiveFormat(contentType)
+	return err
+}
+
 type archiveKind int
 
 const (