Improve documentation of groups endpoint

app/queries/groups/summary_query.rb

@@ -10,7 +10,7 @@ module Groups
 
     def query
       <<~SQL.squish
-        SELECT#{' '}
+        SELECT
           groups.id,
           groups.name,
           groups.icon,

spec/requests/groups_spec.rb

@@ -5,15 +5,26 @@ require 'swagger_helper'
 RSpec.describe 'groups', type: :request do
   path '/groups' do
     get('list groups') do
+      produces 'application/json'
       response(200, 'successful') do
-
-        after do |example|
-          example.metadata[:response][:content] = {
-            'application/json' => {
-              example: JSON.parse(response.body, symbolize_names: true)
+        schema type: :array,
+               items: {
+                 type: :object,
+                 required: %i[id name icon parent_id color total considered invited confirmed declined tentative],
+                 properties: {
+                   id: { type: :string, format: :uuid, required: true },
+                   name: { type: :string },
+                   icon: { type: :string, example: 'pi pi-crown', description: 'The CSS classes used by the icon' },
+                   parent_id: { type: :string, format: :uuid },
+                   color: { type: :string, pattern: '^#(?:[0-9a-fA-F]{3}){1,2}$' },
+                   total: { type: :integer, minimum: 0, description: 'Total number of guests in any status' },
+                   considered: { type: :integer, minimum: 0 },
+                   invited: { type: :integer, minimum: 0 },
+                   confirmed: { type: :integer, minimum: 0 },
+                   declined: { type: :integer, minimum: 0 },
+                   tentative: { type: :integer, minimum: 0 }
                  }
                }
-        end
         run_test!
       end
     end