Add presence validations for required fields (#545)

* Adds basic validations for required fields

Also deletes a few extraneous .keep files

Does not add the family_id required field for user, since that breaks the basic test setup

* Restore keep files to this branch

* Remove Credit model and validate models behind ids

* Restore concerns .keep

app/models/transaction.rb

@@ -2,6 +2,8 @@ class Transaction < ApplicationRecord
   belongs_to :account
   belongs_to :category, optional: true
 
+  validates :name, :date, :amount, :account, presence: true
+
   after_commit :sync_account
 
   def self.ransackable_attributes(auth_object = nil)