Volo.Docs module encounter an ERR_TOO_MANY_REDIRECTS error when the defaultUICulture not in `AbpLocalizationOptions` languages list

[zhchlmm]

• ABP Framework version 3.0.4.
• User Interface MVC
• ABP Module Volo.Docs
• Browser Version Chrome V84

I installed the module Volo.Docs and just want zh-Hans LanguageInfo, so i didn't add en and others LanguageInfo.

private void ConfigureLocalizationServices()
{
    Configure<AbpLocalizationOptions>(options =>
    {
        var resource = options.Resources
        .Get<KnowledgePayResource>()
        .AddBaseTypes(typeof(AbpUiResource));

        //options.Languages.Add(new LanguageInfo("en", "en", "English"));
        options.Languages.Add(new LanguageInfo("zh-Hans", "zh-Hans", "简体中文"));
        //options.Languages.Add(new LanguageInfo("zh-Hant", "zh-Hant", "繁體中文"));

    });
}

When i visit a github repo doc project, an ERR_TOO_MANY_REDIRECTS error was encountered.
It redirect betwwen /documents/en/abp/latest/ and /Abp/Languages/Switch?culture=en&uiCulture=en&returnUrl=/documents/en/abp/latest/ endlessly.

[yekalkan]

If you are using ABP docs, it sets English as default.

See https://github.com/abpframework/abp/blob/dev/docs/docs-langs.json

Getting error is pretty normal in this situation. But we have to explain what is wrong with the configuration, rather than a redirect error.

[zhchlmm]

Related to #4895