Add Account Model specs (#341)

app/models/account.rb

@@ -3,7 +3,7 @@
 # Table name: accounts
 #
 #  id         :integer          not null, primary key
-#  name       :string
+#  name       :string           not null
 #  created_at :datetime         not null
 #  updated_at :datetime         not null
 #
@@ -11,6 +11,8 @@
 class Account < ApplicationRecord
   include Events::Types
 
+  validates :name, presence: true
+
   has_many :users, dependent: :destroy
   has_many :inboxes, dependent: :destroy
   has_many :conversations, dependent: :destroy