Ionic 2 cannot send messages to asp dotnet core even with CORS enabled

I tried to find an answer, some are close, but not what I'm looking for.

This is my problem, I am developing an Ionic app and am currently viewing the view in a web browser. I am unable to post any content back to my main dotnet asp server.

My stack looks like this: Front-End

• Ionic 2 - Latest version using latest Angular 4
• Nginx - as my proxy
• Docker - how my container works with dotnet core apps

Here is the code for the post I'm trying:

let body =JSON.stringify({ 'username': username, 'password': password }); 
let options = new RequestOptions({headers:new Headers()});
options.headers.set('Content-Type', 'application/json; charset=UTF-8');
options.headers.set( 'Accept', 'application/json' );

return this.http.post(this.loginUrl,body,options)
  .map((res: Response) => res.json())
  .catch((error: any) => {
    console.log("ERROR", error);
    return Observable.throw(error.json().error || 'Server error')
  })

      

        
        
        
      

    

My proxy has

add_header 'Access-Control-Allow-Origin' *;

      

        
        
        
      

    

And my support has the following CORS configuration in Startup.cs

            options.AddPolicy("CorsPolicy",
            builder => builder.AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader()
                .AllowCredentials());
        });

      

        
        
        
      

    

and in the Configure function

            app.UseMvc().UseCors("CorsPolicy");

      

        
        
        
      

    

In the Visual Studio 2017 output window, I see the response reaching the container:

Application Insights Telemetry (unconfigured): {"name":"Microsoft.ApplicationInsights.Dev.Request","time":"2017-07-15T19:29:10.5330300Z","tags":{"ai.internal.nodeName":"9a9595bd67c1","ai.operation.id":"0HL6BMO90PHKC","ai.application.ver":"1.0.0.0","ai.operation.name":"OPTIONS Users/AuthenticateUser","ai.internal.sdkVersion":"aspnet5c:2.0.0","ai.cloud.roleInstance":"9a9595bd67c1","ai.location.ip":"172.18.0.5"},"data":{"baseType":"RequestData","baseData":{"ver":2,"id":"HKmnWfByHeU=","name":"OPTIONS Users/AuthenticateUser","duration":"00:00:11.2837000","success":false,"responseCode":"415","url":"http://leo.users/users/authenticate","properties":{"DeveloperMode":"true","httpMethod":"OPTIONS","AspNetCoreEnvironment":"Development"}}}}

      

        
        
        
      

    

I tried several ways to set headers on the Ionic 2 side. I'm not sure what to do / if I just missed something. Help would be much appreciated.

thank