title: Missing method in EnableCorsAttribute
body: <p>I want to enable CORS from my controller into asp.net core 2 application, so into controller I add attribute like:</p>
  
  <pre><code>[EnableCors(origins: "*", headers: "accept,content-type,origin,x-my-header", methods: "*")]
  </code></pre>
  
  <p>But I get error on origins:</p>
  
  <blockquote>
    <p>The best overload for 'EnableCorsAttribute' does not have a parameter
    named 'origins'</p>
  </blockquote>
  
  <p>So I access to EnableCorsAttribute from meta data and I found this methods:</p>
  
  <pre><code>namespace Microsoft.AspNetCore.Cors
  {
  
      public class EnableCorsAttribute : Attribute, IEnableCorsAttribute
      {
          public EnableCorsAttribute(string policyName);
  
          public string PolicyName { get; set; }
      }
  }
  </code></pre>
  
  <p>But is supposly it be a method like this:</p>
  
  <pre><code>public EnableCorsAttribute(string origins, string headers, string methods);
  </code></pre>
  
  <p>Why I don't have it? I need to install something? I'm new in Asp.Net Core and I don't understand why that method isn't in my api. Regards</p>