fix: handle form-urlencoded content type

The default header by curl is application/x-www-form-urlencoded, so when
we send a secret without a specific header this was saved and then
served by the server on secret read.
Set the default content to the requested data when the content type
header was set to form-urlencoded

internal/parsers/createentry.go

@@ -51,7 +51,7 @@ func parseMultiForm(r *http.Request) ([]byte, string, error) {
 
 func getContentType(r *http.Request) string {
 	ct := r.Header.Get("content-type")
-	if ct == "" {
+	if ct == "" || ct == "application/x-www-form-urlencoded" {
 		ct = "application/octet-stream"
 	}