Feature/use hcaptcha if bot (#1476)

* Add captcha to login models and methods

* Add captcha web auth to login

* Extract captcha to abstract base class

* Add Captcha to register

* Null out captcha token after each successful challenge

* Cancel > close

src/Core/Models/Domain/AuthResult.cs

@@ -6,6 +6,8 @@ namespace Bit.Core.Models.Domain
     public class AuthResult
     {
         public bool TwoFactor { get; set; }
+        public bool CaptchaNeeded => !string.IsNullOrWhiteSpace(CaptchaSiteKey);
+        public string CaptchaSiteKey { get; set; }
         public bool ResetMasterPassword { get; set; }
         public Dictionary<TwoFactorProviderType, Dictionary<string, object>> TwoFactorProviders { get; set; }
     }