Create estimate on issue close.

app/models/line_item.rb

@@ -14,4 +14,17 @@ class LineItem < ApplicationRecord
   validates :description, presence: true
   validates :quantity, numericality: { greater_than: 0 }
   validates :unit_price, numericality: { greater_than_or_equal_to: 0 }
+  before_save :total
+
+  private
+
+  def total
+    log "Updating line total"
+    self.line_total = self.unit_price * self.quantity
+  end
+
+  def log(msg)
+    Rails.logger.info "[LineItem] #{msg}"
+  end
+
 end