// AccountController.cs

[Route("/account"), ApiController]
public class AccountController : ControllerBase
{
    [HttpPost("backendLogin"), AllowAnonymous]
    public async Task<ActionResult<LoginResponse>> BackendLogin(LoginRequest lr)
    {
        await Task.CompletedTask.ConfigureAwait(false); // do some business logic
        return Ok(new LoginResponse {UserId = "123"});
    }

    // Models

    public class LoginRequest {
        public string Email { get; set; }
        public string Password { get; set; }
    }

    public class LoginResponse {
        public string UserId { get; set; }
    }
}

// Startup.cs

public void ConfigureServices(IServiceCollection services) {
    services.AddMvcCore()
                    .AddJsonFormatters(settings => {
                        settings.DateTimeZoneHandling = DateTimeZoneHandling.Utc;
                        settings.DateFormatHandling = DateFormatHandling.IsoDateFormat;
                        settings.ContractResolver = new CamelCasePropertyNamesContractResolver();
                    })
                    .SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

    services.Configure<ApiBehaviorOptions>(options => {
        // options.SuppressConsumesConstraintForFormFileParameters = true;
        // options.SuppressInferBindingSourcesForParameters = true;
        // options.SuppressModelStateInvalidFilter = true;
    });
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env) {
    if (env.IsDevelopment()) {
        app.UseDeveloperExceptionPage();
    }
    app.UseMvc();
}