MM-12855 Plugin Context (#9922)

* Basic plugin context.

* Adding more useful fields to plugin context.

* Fix spelling

Co-Authored-By: crspeller <crspeller@gmail.com>

* Fixing location of context creation.

app/file.go

@@ -462,7 +462,7 @@ func (a *App) DoUploadFileExpectModification(now time.Time, rawTeamId string, ra
 
 	if pluginsEnvironment := a.GetPluginsEnvironment(); pluginsEnvironment != nil {
 		var rejectionError *model.AppError
-		pluginContext := &plugin.Context{}
+		pluginContext := a.PluginContext()
 		pluginsEnvironment.RunMultiPluginHook(func(hooks plugin.Hooks) bool {
 			var newBytes bytes.Buffer
 			replacementInfo, rejectionReason := hooks.FileWillBeUploaded(pluginContext, info, bytes.NewReader(data), &newBytes)