add db factory class into the module template.

Oqtane.Server/wwwroot/Modules/Templates/External/Server/Repository/[Module]DbContextFactory.cs

@@ -0,0 +1,25 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+using Oqtane.Infrastructure;
+
+namespace [Owner].Module.[Module].Repository
+{
+    public class [Module]DbContextFactory : IServerStartup
+    {
+        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
+        {
+            // not implemented
+        }
+
+        public void ConfigureMvc(IMvcBuilder mvcBuilder)
+        {
+            // not implemented
+        }
+
+        public void ConfigureServices(IServiceCollection services)
+        {
+            services.AddDbContextFactory<[Module]Context>(opt => { }, ServiceLifetime.Transient);
+        }
+    }
+}