Handle legacy parameters for further education filters in v2/results

This commit updates the handling of legacy
parameters (`age_group` and `qualification`) to ensure compatibility
when filtering by "further education" in the old v1 `/results` endpoint.

- **SearchCoursesForm**:
  - Introduced `age_group` and `qualification` attributes.
  - Added methods to map old parameters (`age_group: 'further_education'` or `qualification: ['pgce pgde']`) to the `level: 'further_education'` parameter.
  - Ensures `search_params` excludes legacy parameters while still applying their equivalent filtering logic.

- **CoursesQuery**:
  - Simplified logic for `further_education_scope` to focus on `level: 'further_education'`.

If a user selects "further education" in the updated v2 filters,
legacy v1 requests using

1. `age_group = further_education` (v1 second question)
2. `qualification = ['pgce pgde']` will continue to work. (v1
   qualification filter when user chooses further education).

This ensures backward compatibility while moving towards the new parameter
conventions.

app/controllers/find/v2/results_controller.rb

@@ -20,9 +20,11 @@ def search_courses_params
           :applications_open,
           :level,
           :funding,
+          :age_group,
           subjects: [],
           study_types: [],
           qualifications: [],
+          qualification: [],
           funding: []
         )
       end

app/forms/search_courses_form.rb

@@ -12,8 +12,21 @@ class SearchCoursesForm < ApplicationForm
   attribute :level
   attribute :funding
 
+  attribute :age_group
+  attribute :qualification
+
   def search_params
-    attributes.symbolize_keys.compact
+    attributes
+      .symbolize_keys
+      .then { |params| params.except(*old_parameters) }
+      .then { |params| transform_old_parameters(params) }
+      .compact
+  end
+
+  def level
+    return 'further_education' if old_further_education_parameters?
+
+    super
   end
 
   def secondary_subjects
@@ -22,4 +35,20 @@ def secondary_subjects
       .where.not(subject_name: ['Modern Languages'])
       .order(:subject_name)
   end
+
+  private
+
+  def transform_old_parameters(params)
+    params.tap do
+      params[:level] = level
+    end
+  end
+
+  def old_further_education_parameters?
+    age_group == 'further_education' || qualification == ['pgce pgde']
+  end
+
+  def old_parameters
+    %i[age_group qualification]
+  end
 end

app/services/courses_query.rb

@@ -93,7 +93,7 @@ def qualifications_scope
   end
 
   def further_education_scope
-    return @scope if params[:level].blank? || params[:level] != 'further_education'
+    return @scope if params[:level] != 'further_education'
 
     @applied_scopes[:level] = params[:level]
 

spec/forms/search_courses_form_spec.rb

@@ -77,8 +77,8 @@
         end
       end
 
-      context 'when old qualification params is used' do
-        let(:form) { described_class.new(qualification: ['']) }
+      context 'when old qualification params is used as string' do
+        let(:form) { described_class.new(qualification: ['pgce pgde']) }
 
         it 'returns level search params' do
           expect(form.search_params).to eq({ level: 'further_education' })

spec/system/find/v2/results/search_results_enabled_spec.rb

@@ -51,13 +51,32 @@
     and_i_see_that_there_are_two_courses_found
   end
 
-  scenario 'when I filter by further education only courses' do
-    given_there_are_courses_containing_all_levels
-    when_i_visit_the_find_results_page
-    and_i_filter_by_further_education_courses
-    then_i_see_only_further_education__courses
-    and_the_further_education_filter_is_checked
-    and_i_see_that_there_is_one_course_found
+  context 'when I filter by further education only courses' do
+    before do
+      given_there_are_courses_containing_all_levels
+    end
+
+    scenario 'when I filter by further education only courses' do
+      when_i_visit_the_find_results_page
+      and_i_filter_by_further_education_courses
+      then_i_see_only_further_education__courses
+      and_the_further_education_filter_is_checked
+      and_i_see_that_there_is_one_course_found
+    end
+
+    scenario 'when I filter by the old age group further education parameter' do
+      when_i_visit_the_find_results_page_using_the_old_age_group_parameter
+      then_i_see_only_further_education__courses
+      and_the_further_education_filter_is_checked
+      and_i_see_that_there_is_one_course_found
+    end
+
+    scenario 'when I filter by the old pgce pgde further education parameter' do
+      when_i_visit_the_find_results_page_using_the_old_pgce_pgde_parameter
+      then_i_see_only_further_education__courses
+      and_the_further_education_filter_is_checked
+      and_i_see_that_there_is_one_course_found
+    end
   end
 
   scenario 'when I filter by applications open' do
@@ -249,6 +268,14 @@ def when_i_visit_the_find_results_page_passing_mathematics_in_the_params
     visit(find_v2_results_path(subjects: ['G1']))
   end
 
+  def when_i_visit_the_find_results_page_using_the_old_age_group_parameter
+    visit(find_v2_results_path(age_group: 'further_education'))
+  end
+
+  def when_i_visit_the_find_results_page_using_the_old_pgce_pgde_parameter
+    visit(find_v2_results_path(qualification: ['pgce pgde']))
+  end
+
   def and_i_search_for_the_mathematics_option
     page.find('[data-filter-search-target="searchInput"]').set('Math')
   end