Extract component for admin officers table

This way we can remove duplication and simplify the code in the view.

Note we're not using the "within" method in the tests to access a row,
because it doesn't seem to work in components tests when passing the
`text:` option.

spec/components/admin/poll/officers/officers_component_spec.rb

@@ -0,0 +1,35 @@
+require "rails_helper"
+
+describe Admin::Poll::Officers::OfficersComponent, type: :component do
+  let(:existing_officer) { create(:poll_officer, name: "Old officer") }
+  let(:new_officer) { build(:poll_officer, name: "New officer") }
+  let(:officers) { [existing_officer, new_officer] }
+  let(:component) { Admin::Poll::Officers::OfficersComponent.new(officers) }
+
+  it "renders as many rows as officers" do
+    within "tbody" do
+      expect(page).to have_css "tr", count: 2
+      expect(page).to have_css "a", count: 2
+    end
+  end
+
+  it "renders link to destroy for existing officers" do
+    render_inline component
+    row = page.find("tr", text: "Old officer")
+
+    expect(row).to have_css "a[data-method='delete']", text: "Delete"
+  end
+
+  it "renders link to add for new officers" do
+    render_inline component
+    row = page.find("tr", text: "New officer")
+
+    expect(row).to have_css "a[data-method='post']", text: "Add"
+  end
+
+  it "accepts table options" do
+    render_inline Admin::Poll::Officers::OfficersComponent.new(officers, class: "my-officers-table")
+
+    expect(page).to have_css "table.my-officers-table"
+  end
+end