In version 6.0.0-rc.7, the GitLabForm class has a method withParam(String name, List<T> values, boolean required) for handling lists of values. However, this method overrides the previously added values in the list when adding parameters to formValues. As a result, only the last value from the list is retained.

Problematic Code

for (T value : values) {
    if (value != null) {
        formValues.put(name + "[]", value.toString());
    }
}

In the above code, formValues.put() is used. Since Map does not allow duplicate keys, each new value with the same key (name + "[]") overrides the previous one.

Expected Behavior

The method should allow multiple values for the same parameter (e.g., appending to a list instead of overwriting). This is required for correctly sending form or query parameters like name[]=value1&name[]=value2.

Actual Behavior

Only the last value from the list is added to formValues.

Steps to Reproduce

1. Create an instance of GitLabForm.
2. Call withParam("names", Arrays.asList("value1", "value2", "value3")).
3. Retrieve getFormValues() and check the result.

Sample Code:

GitLabForm form = new GitLabForm();
form.withParam("names", Arrays.asList("value1", "value2", "value3"));
System.out.println(form.getFormValues());

Actual Output:

{names[]=value3}

Expected Output:

{names[]=[value1, value2, value3]}