Add the ability for Rooms to have a URL.

The URL is shown on the schedule and the event/proposal page.
The URL is only when a user is logged in and registered.

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_03_31_214534) do
+ActiveRecord::Schema.define(version: 2020_07_10_215300) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -406,6 +406,7 @@ ActiveRecord::Schema.define(version: 2020_03_31_214534) do
     t.string "name", null: false
     t.integer "size"
     t.integer "venue_id", null: false
+    t.text "url"
   end
 
   create_table "schedules", force: :cascade do |t|