Use full precision timestamps in JSON serializations

In forms-api PR govuk-forms/forms-api#790 we increased the precision of
timestamps when serializing to the maximum; we should do the same in
forms-admin.

Author: lfdebrux

config/application.rb

@@ -65,5 +65,8 @@ class Application < Rails::Application
 
     # Prevent ActiveRecord::PreparedStatementCacheExpired errors when adding columns
     config.active_record.enumerate_columns_in_select_statements = true
+
+    # Include full precision of timestamps in JSON responses
+    config.active_support.time_precision = 6
   end
 end

spec/requests/forms/make_live_controller_spec.rb

@@ -130,7 +130,7 @@
 
         it "sets the FormDocument's live_at time to be equal to the form's updated_at time" do
           post(make_live_path(form_id: form.id), params: form_params)
-          expect(FormDocument.find_by(form_id: form.id, tag: "live")["content"]["live_at"]).to eq form.reload.updated_at.strftime("%Y-%m-%dT%H:%M:%S.%LZ")
+          expect(FormDocument.find_by(form_id: form.id, tag: "live")["content"]["live_at"]).to eq form.reload.updated_at.strftime("%Y-%m-%dT%H:%M:%S.%6NZ")
         end
       end
 

spec/services/form_document_sync_service_spec.rb

@@ -7,7 +7,7 @@
   describe "#synchronize_form" do
     context "when form state is live" do
       let(:form) { create(:form, :live) }
-      let(:expected_live_at) { form.reload.updated_at.strftime("%Y-%m-%dT%H:%M:%S.%LZ") }
+      let(:expected_live_at) { form.reload.updated_at.strftime("%Y-%m-%dT%H:%M:%S.%6NZ") }
 
       context "when there is no existing form document" do
         it "creates a live form document" do
@@ -32,7 +32,7 @@
 
         it "updates the live_at date in the form document" do
           service.synchronize_form(form)
-          expect(FormDocument.last["content"]).to include("live_at" => form.reload.updated_at.strftime("%Y-%m-%dT%H:%M:%S.%LZ"))
+          expect(FormDocument.last["content"]).to include("live_at" => form.reload.updated_at.strftime("%Y-%m-%dT%H:%M:%S.%6NZ"))
         end
       end