Merge branch 'add_uniqueness_validation_to_user_token' into 'develop'

Validates user token uniqueness

See merge request gtt/redmine_expo_push!1

Author: jkraemer

app/models/expo_push_token.rb

@@ -2,6 +2,7 @@ class ExpoPushToken < ActiveRecord::Base
   belongs_to :user
 
   validates_presence_of :token
+  validates_uniqueness_of :token
   validates_presence_of :user
 end