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

spec/factories/users.rb

@@ -2,13 +2,21 @@
 
 FactoryBot.define do
   factory :user do
+    transient do
+      skip_confirmation { true }
+    end
+
     provider { 'email' }
     uid { SecureRandom.uuid }
-    name { 'John Smith' }
-    nickname { 'jsmith' }
-    email { 'john.smith@example.com' }
+    name { FFaker::Name.name }
+    nickname { FFaker::InternetSE.user_name_from_name(name) }
+    email { nickname + '@example.com' }
     role { 'agent' }
     password { "password" }
     account
+
+    after(:build) do |user, evaluator|
+      user.skip_confirmation! if evaluator.skip_confirmation
+    end
   end
 end