Add location guidance

app/models/form/lettings/pages/location.rb

@@ -7,6 +7,7 @@ class Form::Lettings::Pages::Location < ::Form::Page
         "scheme_has_multiple_locations?" => true,
       },
     ]
+    @header = "Location"
     @next_unresolved_page_id = :check_answers
   end
 

app/models/form/lettings/questions/location_id.rb

@@ -13,6 +13,7 @@ class Form::Lettings::Questions::LocationId < ::Form::Question
     }
     @question_number = 10
     @disable_clearing_if_not_routed_or_dynamic_answer_options = true
+    @top_guidance_partial = "finding_location"
   end
 
   def answer_options

app/views/form/guidance/_finding_location.erb

@@ -0,0 +1,4 @@
+<%= govuk_details(summary_text: "What is a location?") do %>
+  <p class="govuk-body">A location is a postcode where supported housing is provided under a scheme. A scheme can have multiple locations, and a location can have multiple units at the same postcode.</p>
+  <p class="govuk-body"><%= govuk_link_to("Read more about how schemes and locations", scheme_changes_path) %></p>
+<% end %>

spec/models/form/lettings/pages/location_spec.rb

@@ -26,7 +26,7 @@ RSpec.describe Form::Lettings::Pages::Location, type: :model do
   end
 
   it "has the correct header" do
-    expect(page.header).to be_nil
+    expect(page.header).to eq("Location")
   end
 
   it "has the correct description" do