public class DBContextWithUserAuditing : IdentityDbContext<ApplicationUser, ApplicationRole, string>
{
    public string UserId { get; set; }
    public int? TenantId { get; set; }

    public DBContextWithUserAuditing(DbContextOptions<DBContextWithUserAuditing> options) : base(options) { }

    // here we declare our db sets

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.NamesToSnakeCase(); // PostgreSQL
        modelBuilder.EnableSoftDelete();
    }

    public override int SaveChanges()
    {
        ChangeTracker.DetectChanges();
        ChangeTracker.ProcessModification(UserId);
        ChangeTracker.ProcessDeletion(UserId);
        ChangeTracker.ProcessCreation(UserId, TenantId);

        return base.SaveChanges();
    }

    public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        ChangeTracker.DetectChanges();
        ChangeTracker.ProcessModification(UserId);
        ChangeTracker.ProcessDeletion(UserId);
        ChangeTracker.ProcessCreation(UserId, TenantId);

        return (await base.SaveChangesAsync(true, cancellationToken));
    }
}

public class AppInitializerFilter : IAsyncActionFilter
{
    private Session _session;
    private DBContextWithUserAuditing _dbContext;
    private ITenantService _tenantService;

    public AppInitializerFilter(
        DBContextWithUserAuditing dbContext
        )
    {
        _dbContext = dbContext;
    }

    public async Task OnActionExecutionAsync(
        ActionExecutingContext context,
        ActionExecutionDelegate next
        )
    {
        string userId = null;
        int? tenantId = null;

        var claimsIdentity = (ClaimsIdentity)context.HttpContext.User.Identity;

        var userIdClaim = claimsIdentity.Claims.SingleOrDefault(c => c.Type == ClaimTypes.NameIdentifier);
        if (userIdClaim != null)
        {
            userId = userIdClaim.Value;
        }

        var tenantIdClaim = claimsIdentity.Claims.SingleOrDefault(c => c.Type == CustomClaims.TenantId);
        if (tenantIdClaim != null)
        {
            tenantId = !string.IsNullOrEmpty(tenantIdClaim.Value) ? int.Parse(tenantIdClaim.Value) : (int?)null;
        }

        _dbContext.UserId = userId;
        _dbContext.TenantId = tenantId;

        var resultContext = await next();
    }
}

services
    .AddMvc(options =>
    {
        options.Filters.Add(typeof(OnRequestInit));
    })

public static class ChangeTrackerExtensions
{
    public static void ProcessCreation(this ChangeTracker changeTracker, string userId, int? tenantId)
    {
        foreach (var item in changeTracker.Entries<IHasCreationTime>().Where(e => e.State == EntityState.Added))
        {
            item.Entity.CreationTime = DateTime.Now;
        }

        foreach (var item in changeTracker.Entries<IHasCreatorUserId>().Where(e => e.State == EntityState.Added))
        {
            item.Entity.CreatorUserId = userId;
        }

        foreach (var item in changeTracker.Entries<IMustHaveTenant>().Where(e => e.State == EntityState.Added))
        {
            if (tenantId.HasValue)
            {
                item.Entity.TenantId = tenantId.Value;
            }
        }
    }