CLDC-1457 Update checkbox validation message (#1207)

app/models/form/sales/questions/buyers_organisations.rb

@@ -15,4 +15,8 @@ class Form::Sales::Questions::BuyersOrganisations < ::Form::Question
     "pregla" => { "value" => "Local Authority" },
     "pregghb" => { "value" => "Help to Buy Agent" },
   }.freeze
+
+  def unanswered_error_message
+    "At least one option must be selected of these four"
+  end
 end

spec/models/form/sales/questions/buyers_organisations_spec.rb

@@ -35,6 +35,10 @@ RSpec.describe Form::Sales::Questions::BuyersOrganisations, type: :model do
     expect(question.hint_text).to eq("Select all that apply")
   end
 
+  it "has the correct unanswered_error_message" do
+    expect(question.unanswered_error_message).to eq("At least one option must be selected of these four")
+  end
+
   it "has the correct answer_options" do
     expect(question.answer_options).to eq(
       {