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/MediaRepository.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text.RegularExpressions;
@@ -407,13 +407,10 @@ namespace Umbraco.Cms.Infrastructure.Persistence.Repositories.Implement
             return _mediaByGuidReadRepository.Exists(id);
         }
 
-        /// <summary>
-        /// A reading repository purely for looking up by GUID
-        /// </summary>
-        /// <remarks>
-        /// TODO: This is ugly and to fix we need to decouple the IRepositoryQueryable -> IRepository -> IReadRepository which should all be separate things!
-        /// Then we can do the same thing with repository instances and we wouldn't need to leave all these methods as not implemented because we wouldn't need to implement them
-        /// </remarks>
+        
+        // A reading repository purely for looking up by GUID
+        // TODO: This is ugly and to fix we need to decouple the IRepositoryQueryable -> IRepository -> IReadRepository which should all be separate things!
+        // This sub-repository pattern is super old and totally unecessary anymore, caching can be handled in much nicer ways without this        
         private class MediaByGuidReadRepository : EntityRepositoryBase<Guid, IMedia>
         {
             private readonly MediaRepository _outerRepo;
@@ -424,8 +421,6 @@ namespace Umbraco.Cms.Infrastructure.Persistence.Repositories.Implement
                 _outerRepo = outerRepo;
             }
 
-            protected override Guid NodeObjectTypeId => _outerRepo.NodeObjectTypeId;
-
             protected override IMedia PerformGet(Guid id)
             {
                 var sql = _outerRepo.GetBaseQuery(QueryType.Single)