Set the CurrentUser when doing imports

The `Import()` extension method provided by the Data Transfer Library doesn't have access to the `HttpContext` and, thus, can't set the `LastModifiedBy` to the current user if that option is selected via the editor (see #5361a8e). This can be mitigated by injecting that value into the `ImportOptions` object prior to import. Note that this behavior is by design, but it does require this configuration from callers to ensure that it works correctly.

Author: JeremyCaney

OnTopic.Editor.AspNetCore/Controllers/EditorController.cs

@@ -649,10 +649,12 @@ public async Task<IActionResult> Import(IFormFile jsonFile, [Bind(Prefix = "Impo
       \-----------------------------------------------------------------------------------------------------------------------*/
       var editorViewModel       = await GetEditorViewModel<ImportViewModel>(contentTypeDescriptor, false, false);
 
+      options.CurrentUser       = HttpContext.User.Identity.Name?? "System";
+
       editorViewModel.ImportOptions = options;
 
       /*------------------------------------------------------------------------------------------------------------------------
-      | Validate parameters
+      | VALIDATE PARAMETERS
       \-----------------------------------------------------------------------------------------------------------------------*/
       if (jsonFile == null) {
         ModelState.AddModelError("jsonFile", "The JSON file is required to import data.");