Plan And Price Updates (#859)

* Expanded the Plan model to make plan & product data a bit more dynamic 
* Created a Product enum to track versioned instances of the same plan
* Created and API call and Response model for getting plan & product data from the server

src/Api/Controllers/PlansController.cs

@@ -0,0 +1,21 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Bit.Core.Utilities;
+using Bit.Core.Models.Api;
+using System.Linq;
+
+namespace Bit.Api.Controllers
+{
+    [Route("plans")]
+    [Authorize("Web")]
+    public class PlansController : Controller
+    {
+        [HttpGet("")]
+        public ListResponseModel<PlanResponseModel> Get()
+        {
+            var data = StaticStore.Plans;
+            var responses = data.Select(plan => new PlanResponseModel(plan));
+            return new ListResponseModel<PlanResponseModel>(responses);
+        }
+    }
+}