Allow user to add buy and sell trade transactions for investment accounts (#1066)

* Consolidate modal form structure into partial + helper

* Scaffold out trade transaction form

* Normalize translations

* Add buy and sell trade form with tests

* Move entryable lists to dedicated controllers

* Delegate entry group contents rendering

* More cleanup

* Extract transaction and valuation update logic from entries controller

* Delegate edit and show actions to entryables

* Trade builder

* Update paths for transaction updates

app/models/account/trade_builder.rb

@@ -0,0 +1,46 @@
+class Account::TradeBuilder
+  TYPES = %w[ buy sell ].freeze
+
+  include ActiveModel::Model
+
+  attr_accessor :type, :qty, :price, :ticker, :date, :account
+
+  validates :type, :qty, :price, :ticker, :date, presence: true
+  validates :price, numericality: { greater_than: 0 }
+  validates :type, inclusion: { in: TYPES }
+
+  def save
+    if valid?
+      create_entry
+    end
+  end
+
+  private
+
+    def create_entry
+      account.entries.account_trades.create! \
+        date: date,
+        amount: amount,
+        currency: account.currency,
+        entryable: Account::Trade.new(
+          security: security,
+          qty: signed_qty,
+          price: price.to_d,
+          currency: account.currency
+        )
+    end
+
+    def security
+      Security.find_or_create_by(ticker: ticker)
+    end
+
+    def amount
+      price.to_d * signed_qty
+    end
+
+    def signed_qty
+      _qty = qty.to_d
+      _qty = _qty * -1 if type == "sell"
+      _qty
+    end
+end