Add an adapter for search-api-v2

In the short-term, `search-api-v2` will exist alongside the current `search-api` service.
`search-api-v2` provides a compatible API for pure search (GET requests) so the adapter is
almost equivalent to `search-api`. The reasoning for this is so that, from a consuming
service's perspective, the search interface is the same.

lib/gds_api.rb

@@ -16,6 +16,7 @@
 require "gds_api/publishing_api"
 require "gds_api/router"
 require "gds_api/search"
+require "gds_api/search_api_v2"
 require "gds_api/support"
 require "gds_api/support_api"
 require "gds_api/worldwide"

lib/gds_api/search_api_v2.rb

@@ -0,0 +1,8 @@
+module GdsApi
+  class SearchApiV2 < Base
+    def search(args, additional_headers = {})
+      request_url = "#{endpoint}/search.json?#{Rack::Utils.build_nested_query(args)}"
+      get_json(request_url, additional_headers)
+    end
+  end
+end

test/search_api_v2_test.rb

@@ -0,0 +1,80 @@
+require "test_helper"
+require "gds_api/search_api_v2"
+
+describe GdsApi::SearchApiV2 do
+  before(:each) do
+    stub_request(:get, /example.com\/search/).to_return(body: "[]")
+  end
+
+  it "#search should raise an exception if the service at the search URI returns a 500" do
+    stub_request(:get, /example.com\/search.json/).to_return(status: [500, "Internal Server Error"])
+    assert_raises(GdsApi::HTTPServerError) do
+      GdsApi::SearchApiV2.new("http://example.com").search(q: "query")
+    end
+  end
+
+  it "#search should raise an exception if the service at the search URI returns a 404" do
+    stub_request(:get, /example.com\/search/).to_return(status: [404, "Not Found"])
+    assert_raises(GdsApi::HTTPNotFound) do
+      GdsApi::SearchApiV2.new("http://example.com").search(q: "query")
+    end
+  end
+
+  it "#search should raise an exception if the service at the search URI returns a 400" do
+    stub_request(:get, /example.com\/search/).to_return(
+      status: [400, "Bad Request"],
+      body: '"error":"Filtering by \"coffee\" is not allowed"',
+    )
+    assert_raises(GdsApi::HTTPClientError) do
+      GdsApi::SearchApiV2.new("http://example.com").search(q: "query", filter_coffee: "tea")
+    end
+  end
+
+  it "#search should raise an exception if the service at the search URI returns a 422" do
+    stub_request(:get, /example.com\/search/).to_return(
+      status: [422, "Bad Request"],
+      body: '"error":"Filtering by \"coffee\" is not allowed"',
+    )
+    assert_raises(GdsApi::HTTPUnprocessableEntity) do
+      GdsApi::SearchApiV2.new("http://example.com").search(q: "query", filter_coffee: "tea")
+    end
+  end
+
+  it "#search should raise an exception if the service at the search URI times out" do
+    stub_request(:get, /example.com\/search/).to_timeout
+    assert_raises(GdsApi::TimedOutException) do
+      GdsApi::SearchApiV2.new("http://example.com").search(q: "query")
+    end
+  end
+
+  it "#search should return the search deserialized from json" do
+    search_results = [{ "title" => "document-title" }]
+    stub_request(:get, /example.com\/search/).to_return(body: search_results.to_json)
+    results = GdsApi::SearchApiV2.new("http://example.com").search(q: "query")
+    assert_equal search_results, results.to_hash
+  end
+
+  it "#search should request the search results in JSON format" do
+    GdsApi::SearchApiV2.new("http://example.com").search(q: "query")
+
+    assert_requested :get, /.*/, headers: { "Accept" => "application/json" }
+  end
+
+  it "#search should issue a request for all the params supplied" do
+    GdsApi::SearchApiV2.new("http://example.com").search(
+      q: "query & stuff",
+      filter_topics: %w[1 2],
+      order: "-public_timestamp",
+    )
+
+    assert_requested :get, /q=query%20%26%20stuff/
+    assert_requested :get, /filter_topics\[\]=1&filter_topics\[\]=2/
+    assert_requested :get, /order=-public_timestamp/
+  end
+
+  it "#search can pass additional headers" do
+    GdsApi::SearchApiV2.new("http://example.com").search({ q: "query" }, "authorization" => "token")
+
+    assert_requested :get, /.*/, headers: { "authorization" => "token" }
+  end
+end