New table and service to store auth tokens

Implements the auth token retrieval and storage for the identity implementation. This is now automatically done for providers and the back office user manager can be used to retreive and store all tokens.

Fixes locking on the config writer.

Removes the abstract NodeObjectTypeId from the base repo since it shouldn't be there.

src/Umbraco.Infrastructure/Persistence/Repositories/Implement/KeyValueRepository.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.Extensions.Logging;
@@ -33,8 +33,6 @@ namespace Umbraco.Cms.Infrastructure.Persistence.Repositories.Implement
 
         #region Overrides of EntityRepositoryBase<string, IKeyValue>
 
-        protected override Guid NodeObjectTypeId => throw new NotSupportedException();
-
         protected override Sql<ISqlContext> GetBaseQuery(bool isCount)
         {
             var sql = SqlContext.Sql();