Add test for expanded links endpoint
user
```ruby
require "rails_helper"

RSpec.describe "GET /v2/expanded-links/:id", type: :request do
  it "returns expanded links" do
    organisation = create(:content_item,
      state: "published",
      format: "organisation",
      base_path: "/my-super-org",
      content_id: "9b5ae6f5-f127-4843-9333-c157a404dd2d",
    )

    content_item = create(:content_item,
      state: "published",
      format: "placeholder",
      title: "Some title",
    )

    link_set = create(:link_set,
      content_id: content_item.content_id,
    )

    create(:link, link_set: link_set, target_content_id: organisation.content_id, link_type: 'organisations')

    get "/v2/expanded-links/#{content_item.content_id}"

    expect(parsed_response).to eql({
      "organisations" => [
        {
          "analytics_identifier" => "GDS01",
          "api_url" => "http://www.dev.gov.uk/api/content/my-super-org",
          "base_path" => "/my-super-org",
          "content_id" => "9b5ae6f5-f127-4843-9333-c157a404dd2d",
          "description" => "VAT rates for goods and services",
          "locale" => "en",
          "title" => "VAT rates",
          "web_url" => "http://www.dev.gov.uk/my-super-org",
          "expanded_links" => {}
        }
      ]
    })
  end

  it "returns empty expanded links if there are no links" do
    content_item = create(:content_item,
      state: "published",
      format: "placeholder",
      title: "Some title",
    )

    content_item = create(:link_set,
      content_id: content_item.content_id,
    )

    get "/v2/expanded-links/#{content_item.content_id}"

    expect(parsed_response).to eql({})
  end
end
```
assistant