Remove DbConfig and new constructors on DbContextBase and refactor Migrations to use explcit generation of IOqtaneDatabase instance

Oqtane.Server/Repository/Interfaces/IDbConfig.cs

@@ -1,20 +0,0 @@
-using System.Collections.Generic;
-using Microsoft.AspNetCore.Http;
-using Microsoft.Extensions.Configuration;
-using Oqtane.Interfaces;
-
-namespace Oqtane.Repository
-{
-    public interface IDbConfig
-    {
-        public IHttpContextAccessor Accessor { get; }
-
-        public IConfiguration Configuration { get; }
-
-        public IEnumerable<IOqtaneDatabase> Databases { get; set; }
-
-        public string ConnectionString { get; set; }
-
-        public string DatabaseType { get; set; }
-    }
-}