Move method to get available filters to the model

We're naming the method `investments_filters`, with the word
"investments" in plural, to be consistent with the method
`investments_orders`.

app/controllers/concerns/investment_filters.rb

@@ -16,12 +16,6 @@ module InvestmentFilters
   end
 
   def investment_filters
-    [
-      "not_unfeasible",
-      "unfeasible",
-      ("unselected" if @budget.publishing_prices_or_later?),
-      ("selected" if @budget.publishing_prices_or_later?),
-      ("winners" if @budget.finished?)
-    ].compact
+    @budget.investments_filters
   end
 end

app/models/budget.rb

@@ -196,6 +196,16 @@ class Budget < ApplicationRecord
     end
   end
 
+  def investments_filters
+    [
+      "not_unfeasible",
+      "unfeasible",
+      ("unselected" if publishing_prices_or_later?),
+      ("selected" if publishing_prices_or_later?),
+      ("winners" if finished?)
+    ].compact
+  end
+
   def email_selected
     investments.selected.order(:id).each do |investment|
       Mailer.budget_investment_selected(investment).deliver_later

spec/models/budget_spec.rb

@@ -285,6 +285,30 @@ describe Budget do
     end
   end
 
+  describe "#investments_filters" do
+    it "returns feasibility filters before publishing prices" do
+      %w[informing accepting reviewing selecting valuating].each do |phase|
+        budget.phase = phase
+
+        expect(budget.investments_filters).to eq(%w[not_unfeasible unfeasible])
+      end
+    end
+
+    it "returns feasibility and selection filters during the final voting phases" do
+      %w[publishing_prices balloting reviewing_ballots].each do |phase|
+        budget.phase = phase
+
+        expect(budget.investments_filters).to eq(%w[not_unfeasible unfeasible unselected selected])
+      end
+    end
+
+    it "returns all filters after the budget has finished" do
+      budget.phase = "finished"
+
+      expect(budget.investments_filters).to eq(%w[not_unfeasible unfeasible unselected selected winners])
+    end
+  end
+
   describe "#has_winning_investments?" do
     it "returns true if there is a winner investment" do
       budget.investments << build(:budget_investment, :winner, price: 3, ballot_lines_count: 2)