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/Identity/Startup.cs

@@ -4,6 +4,7 @@ using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Configuration;
 using Bit.Core;
+using Bit.Core.Context;
 using Bit.Core.Utilities;
 using AspNetCoreRateLimit;
 using System.Globalization;
@@ -49,7 +50,7 @@ namespace Bit.Identity
             services.AddSqlServerRepositories(globalSettings);
 
             // Context
-            services.AddScoped<CurrentContext>();
+            services.AddScoped<ICurrentContext, CurrentContext>();
 
             // Caching
             services.AddMemoryCache();