Move merchants to top-level namespace (#895)

app/models/merchant.rb

@@ -0,0 +1,10 @@
+class Merchant < ApplicationRecord
+  has_many :transactions, dependent: :nullify
+  belongs_to :family
+
+  validates :name, :color, :family, presence: true
+
+  scope :alphabetically, -> { order(:name) }
+
+  COLORS = %w[#e99537 #4da568 #6471eb #db5a54 #df4e92 #c44fe9 #eb5429 #61c9ea #805dee #6ad28a]
+end