Add ability to set user and context in rce_js_env_base

This improves reusability of the method.

fixes QUIZ-11132
flag=none

test plan:
- add a binding.pry line in WikiPagesController
- try to edit a page in a course, this gives you pry
- ensure rce_js_env_base is callable with and without params

Change-Id: If6ca548dac3c51fb724c168a2c0e000b2bf44af3
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/316756
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Roland Beres <roland.beres@instructure.com>
QA-Review: Roland Beres <roland.beres@instructure.com>
Product-Review: Roland Beres <roland.beres@instructure.com>

app/controllers/application_controller.rb

@@ -392,12 +392,12 @@ class ApplicationController < ActionController::Base
   helper_method :render_js_env
 
   # add keys to JS environment necessary for the RCE at the given risk level
-  def rce_js_env_base(domain: request.host_with_port)
+  def rce_js_env_base(domain: request.host_with_port, user: @current_user, context: @context)
     Services::RichContent.env_for(
-      user: @current_user,
+      user: user,
       domain: domain,
       real_user: @real_current_user,
-      context: @context
+      context: context
     )
   end