Feature/update confirmation email information (#145)

* Add `invited_by` foreign key to User

Allows for a User to be tied to the user who invited them

* Include `current_user` in new agent initialization parameters

* Add `shoulda-matchers` for testing associations

* Add Inviter information and associated account to welcome email

* Only show inviter info if applicable

* Update conversation spec for FFaker compatibility

db/migrate/20191014051743_add_invited_by_to_user.rb

@@ -0,0 +1,5 @@
+class AddInvitedByToUser < ActiveRecord::Migration[6.1]
+  def change
+    add_reference(:users, :inviter, foreign_key: { to_table: :users })
+  end
+end

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: 2019_08_19_010457) do
+ActiveRecord::Schema.define(version: 2019_10_14_051743) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -205,9 +205,12 @@ ActiveRecord::Schema.define(version: 2019_08_19_010457) do
     t.datetime "updated_at", null: false
     t.string "channel"
     t.integer "role", default: 0
+    t.bigint "inviter_id"
     t.index ["email"], name: "index_users_on_email"
+    t.index ["inviter_id"], name: "index_users_on_inviter_id"
     t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
     t.index ["uid", "provider"], name: "index_users_on_uid_and_provider", unique: true
   end
 
+  add_foreign_key "users", "users", column: "inviter_id"
 end