Extract component for supporting budget admin stats

This is consistent with the component for balloting stats. We're about
to change both components, and the changes are easier to follow if
they're similar.

We're also using consistent names in methods.

spec/components/admin/stats/budget_supporting_component_spec.rb

@@ -0,0 +1,51 @@
+require "rails_helper"
+
+describe Admin::Stats::BudgetSupportingComponent do
+  let(:budget) { create(:budget, :balloting) }
+  let(:heading) { create(:budget_heading, budget: budget, name: "Main heading") }
+  let(:investment) { create(:budget_investment, :feasible, :selected, heading: heading) }
+
+  it "shows the number of supports in investment projects" do
+    another_heading = create(:budget_heading, budget: budget)
+    another_investment = create(:budget_investment, heading: another_heading)
+
+    create(:user, :level_two, votables: [investment, another_investment])
+    create(:user, :level_two, votables: [investment])
+    create(:user, :level_two)
+
+    render_inline Admin::Stats::BudgetSupportingComponent.new(budget)
+
+    expect(page).to have_css "p", exact_text: "Votes 3", normalize_ws: true
+  end
+
+  it "shows the number of users that have supported an investment project" do
+    another_heading = create(:budget_heading, budget: budget)
+    another_investment = create(:budget_investment, heading: another_heading)
+
+    create(:user, :level_two, votables: [investment, another_investment])
+    create(:user, :level_two, votables: [investment])
+    create(:user, :level_two)
+
+    render_inline Admin::Stats::BudgetSupportingComponent.new(budget)
+
+    expect(page).to have_css "p", exact_text: "Participants 2", normalize_ws: true
+  end
+
+  it "shows the number of users that have supported investments projects per heading" do
+    group_districts = create(:budget_group, budget: budget)
+    north_district = create(:budget_heading, group: group_districts, name: "North district")
+    create(:budget_heading, group: group_districts, name: "South district")
+
+    create(:budget_investment, heading: heading, voters: [create(:user)])
+    create(:budget_investment, heading: north_district, voters: [create(:user)])
+    create(:budget_investment, heading: north_district, voters: [create(:user)])
+
+    render_inline Admin::Stats::BudgetSupportingComponent.new(budget)
+
+    page.find ".user-count-by-heading tbody" do |table_body|
+      expect(table_body).to have_css "tr", exact_text: "Main heading 1", normalize_ws: true
+      expect(table_body).to have_css "tr", exact_text: "North district 2", normalize_ws: true
+      expect(table_body).to have_css "tr", exact_text: "South district 0", normalize_ws: true
+    end
+  end
+end