Restore filtering investments by milestone status query

This commit makes 3 changes:

1. Extracts a query into a helper for clarity and DRYness

2. Adds a `.where` clause to filter investments based on their
(current) milestone status

3. Fixes a bug where investments would be rendered as many times as
milestones associated to an investment

app/helpers/budget_executions_helper.rb

@@ -0,0 +1,20 @@
+module BudgetExecutionsHelper
+
+  def winner_investments(heading)
+    if params[:status].present?
+      heading.investments
+             .selected
+             .sort_by_ballots
+             .joins(:milestones)
+             .distinct
+             .where('budget_investment_milestones.status_id = ?', params[:status])
+    else
+      heading.investments
+             .selected
+             .sort_by_ballots
+             .joins(:milestones)
+             .distinct
+    end
+  end
+
+end

app/views/budgets/executions/_investments.html.erb

@@ -3,7 +3,7 @@
     <%= heading.name %>
   </h4>
   <div class="row" data-equalizer-on="medium" data-equalizer>
-    <% heading.investments.selected.sort_by_ballots.joins(:milestones).each do |investment| %>
+    <% winner_investments(heading).each do |investment| %>
       <div class="small-12 medium-6 large-4 column end margin-bottom">
         <div class="budget-execution">
           <%= link_to budget_investment_path(@budget, investment, anchor: "tab-milestones"), data: { 'equalizer-watch': true } do %>