Allow users to remove their support on investments

Note we don't cast negative votes when users remove their support. That
way we provide compatibility for institutions who have implemented real
negative votes (in case there are / will be any), and we also keep the
database meaningful: it's not that users downvoted something; they
simply removed their upvote.

Co-Authored-By: Javi Martín <javim@elretirao.net>
Co-Authored-By: Julian Nicolas Herrero <microweb10@gmail.com>

spec/system/management/budget_investments_spec.rb

@@ -333,6 +333,56 @@ describe "Budget Investments" do
       expect(page).to have_content "CONSUL\nMANAGEMENT"
     end
 
+    scenario "Remove support on behalf of someone else in index view" do
+      create(:budget_investment, heading: heading)
+
+      login_managed_user(user)
+      login_as_manager(manager)
+
+      visit management_budget_investments_path(budget)
+      click_button "Support"
+
+      expect(page).to have_content "1 support"
+      expect(page).to have_content "You have already supported this investment project. Share it!"
+      expect(page).not_to have_button "Support"
+
+      click_button "Remove your support"
+
+      expect(page).to have_content "No supports"
+      expect(page).to have_button "Support"
+      expect(page).not_to have_button "Remove your support"
+    end
+
+    scenario "Remove support on behalf of someone else in show view" do
+      create(:budget_investment, heading: heading, title: "Don't support me!")
+
+      login_managed_user(user)
+      login_as_manager(manager)
+
+      visit management_budget_investments_path(budget)
+      click_link "Don't support me!"
+
+      expect(page).to have_css "h1", exact_text: "Don't support me!"
+
+      click_button "Support"
+
+      expect(page).to have_content "1 support"
+      expect(page).to have_content "You have already supported this investment project. Share it!"
+      expect(page).not_to have_button "Support"
+
+      click_button "Remove your support"
+
+      expect(page).to have_content "No supports"
+      expect(page).to have_button "Support"
+      expect(page).not_to have_button "Remove your support"
+
+      refresh
+
+      expect(page).to have_content "No supports"
+      expect(page).to have_button "Support"
+      expect(page).not_to have_button "Remove your support"
+    end
+
     scenario "Should not allow unverified users to vote proposals" do
       login_managed_user(create(:user))
       create(:budget_investment, budget: budget)