Make it possible to select proposals without JavaScript

This way, when JavaScript hasn't loaded (for whatever reason),
administrators can still use this functionality.

spec/controllers/admin/proposals_controller_spec.rb

@@ -0,0 +1,61 @@
+require "rails_helper"
+
+describe Admin::ProposalsController, :admin do
+  describe "PATCH select" do
+    let(:proposal) { create(:proposal) }
+
+    it "selects the proposal" do
+      expect do
+        patch :select, xhr: true, params: { id: proposal.id }
+      end.to change { proposal.reload.selected? }.from(false).to(true)
+
+      expect(response).to be_successful
+    end
+
+    it "does not modify already selected proposals" do
+      proposal.update!(selected: true)
+
+      expect do
+        patch :select, xhr: true, params: { id: proposal.id }
+      end.not_to change { proposal.reload.selected? }
+    end
+
+    it "redirects admins without JavaScript to the same page" do
+      request.env["HTTP_REFERER"] = admin_proposals_path
+
+      patch :select, params: { id: proposal.id }
+
+      expect(response).to redirect_to admin_proposals_path
+      expect(flash[:notice]).to eq "Proposal updated successfully."
+    end
+  end
+
+  describe "PATCH deselect" do
+    let(:proposal) { create(:proposal, :selected) }
+
+    it "deselects the proposal" do
+      expect do
+        patch :deselect, xhr: true, params: { id: proposal.id }
+      end.to change { proposal.reload.selected? }.from(true).to(false)
+
+      expect(response).to be_successful
+    end
+
+    it "does not modify non-selected proposals" do
+      proposal.update!(selected: false)
+
+      expect do
+        patch :deselect, xhr: true, params: { id: proposal.id }
+      end.not_to change { proposal.reload.selected? }
+    end
+
+    it "redirects admins without JavaScript to the same page" do
+      request.env["HTTP_REFERER"] = admin_proposals_path
+
+      patch :deselect, params: { id: proposal.id }
+
+      expect(response).to redirect_to admin_proposals_path
+      expect(flash[:notice]).to eq "Proposal updated successfully."
+    end
+  end
+end