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/security.rb

@@ -0,0 +1,14 @@
+class Security < ApplicationRecord
+  before_save :normalize_identifiers
+
+  has_many :trades, dependent: :nullify, class_name: "Account::Trade"
+
+  validates :isin, presence: true, uniqueness: { case_sensitive: false }
+
+  private
+
+    def normalize_identifiers
+      self.isin = isin.upcase
+      self.symbol = symbol.upcase
+    end
+end