Investment Portfolio Sync (#974)

* Add investment portfolio models

* Add portfolio to demo data

* Setup initial tests

* Rough sketch of sync logic

* Clean up trade sync logic

* Add trade validation

* Integrate trades into sync process

app/models/account/trade.rb

@@ -0,0 +1,26 @@
+class Account::Trade < ApplicationRecord
+  include Account::Entryable
+
+  belongs_to :security
+
+  validates :qty, presence: true, numericality: { other_than: 0 }
+  validates :price, presence: true
+
+  class << self
+    def search(_params)
+      all
+    end
+
+    def requires_search?(_params)
+      false
+    end
+  end
+
+  def sell?
+    qty < 0
+  end
+
+  def buy?
+    qty > 0
+  end
+end