Add disable send policy (#1130)

* Add Disable Send policy

* Test DisableSend policy

* PR Review

* Update tests for using CurrentContext

This required making an interface for CurrentContext and mocking out
the members used. The interface can be expanded as needed for tests.

I moved CurrentContext to a folder, which changes the namespace
and causes a lot of file touches, but most are just adding a reference

* Fix failing test

* Update exemption to include all exempt users

* Move all CurrentContext usages to ICurrentContext

* PR review. Match messaging with Web

src/Api/Controllers/EventsController.cs

@@ -7,7 +7,7 @@ using Microsoft.AspNetCore.Authorization;
 using Bit.Core.Exceptions;
 using Bit.Core.Models.Api;
 using Bit.Core.Services;
-using Bit.Core;
+using Bit.Core.Context;
 using Bit.Core.Models.Data;
 
 namespace Bit.Api.Controllers
@@ -20,14 +20,14 @@ namespace Bit.Api.Controllers
         private readonly ICipherRepository _cipherRepository;
         private readonly IOrganizationUserRepository _organizationUserRepository;
         private readonly IEventRepository _eventRepository;
-        private readonly CurrentContext _currentContext;
+        private readonly ICurrentContext _currentContext;
 
         public EventsController(
             IUserService userService,
             ICipherRepository cipherRepository,
             IOrganizationUserRepository organizationUserRepository,
             IEventRepository eventRepository,
-            CurrentContext currentContext)
+            ICurrentContext currentContext)
         {
             _userService = userService;
             _cipherRepository = cipherRepository;