Upgrade to Rails 6.0 and apply new framework defaults

db/schema.rb

@@ -2,15 +2,15 @@
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
 #
-# Note that this schema.rb definition is the authoritative source for your
-# database schema. If you need to create the application database on another
-# system, you should be using db:schema:load, not running all the migrations
-# from scratch. The latter is a flawed and unsustainable approach (the more migrations
-# you'll amass, the slower it'll run and the greater likelihood for issues).
+# This file is the source Rails uses to define your schema when running `rails
+# db:schema:load`. When creating a new database, `rails db:schema:load` tends to
+# be faster and is potentially less error prone than running all of your
+# migrations from scratch. Old migrations may fail to apply correctly if those
+# migrations use external dependencies or application code.
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2021_04_26_113125) do
+ActiveRecord::Schema.define(version: 2021_05_10_174452) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
@@ -481,7 +481,6 @@ ActiveRecord::Schema.define(version: 2021_04_26_113125) do
   add_foreign_key "exercise_tips", "exercise_tips", column: "parent_exercise_tip_id"
   add_foreign_key "exercise_tips", "exercises"
   add_foreign_key "exercise_tips", "tips"
-  add_foreign_key "request_for_comments", "submissions", name: "request_for_comments_submissions_id_fk"
   add_foreign_key "remote_evaluation_mappings", "study_groups"
   add_foreign_key "submissions", "study_groups"
   add_foreign_key "tips", "file_types"