Change creator_id to only need to be unique for schools where rejecte… (#742)

## Status

-
[Closes](RaspberryPiFoundation/digital-editor-issues#1233)

## What's changed?

- Update school creation validation so that `creator_id` can be reused
if `rejected_at` is not nil

Author: jamiebenstead

app/models/school.rb

@@ -31,7 +31,11 @@ class School < ApplicationRecord
             format: { with: /\A[0-9]+[A-Z]+\z/, allow_nil: true, message: I18n.t('validations.school.school_roll_number') },
             presence: true,
             if: :ireland?
-  validates :creator_id, presence: true, uniqueness: true
+  validates :creator_id,
+            presence: true,
+            uniqueness: {
+              conditions: -> { where(rejected_at: nil) }
+            }
   validates :creator_agree_authority, presence: true, acceptance: true
   validates :creator_agree_terms_and_conditions, presence: true, acceptance: true
   validates :creator_agree_responsible_safeguarding, presence: true, acceptance: true
@@ -52,7 +56,7 @@ class School < ApplicationRecord
   after_create :generate_code!
 
   def self.find_for_user!(user)
-    school = Role.find_by(user_id: user.id)&.school || find_by(creator_id: user.id)
+    school = Role.find_by(user_id: user.id)&.school || find_by(creator_id: user.id, rejected_at: nil)
     raise ActiveRecord::RecordNotFound unless school
 
     school

db/migrate/20260323152328_update_creator_id_index_on_schools.rb

@@ -0,0 +1,20 @@
+class UpdateCreatorIdIndexOnSchools < ActiveRecord::Migration[7.2]
+  def up
+    remove_index :schools, name: "index_schools_on_creator_id"
+
+    add_index :schools,
+              :creator_id,
+              unique: true,
+              where: "rejected_at IS NULL",
+              name: "index_schools_on_creator_id_active_only"
+  end
+
+  def down
+    remove_index :schools, name: "index_schools_on_creator_id_active_only"
+
+    add_index :schools,
+              :creator_id,
+              unique: true,
+              name: "index_schools_on_creator_id"
+  end
+end

db/schema.rb

@@ -483,6 +483,14 @@
       user = build(:user)
       expect { described_class.find_for_user!(user) }.to raise_error(ActiveRecord::RecordNotFound)
     end
+
+    it('raises ActiveRecord::RecordNotFound if the user is the creator of a rejected school') do
+      creator = create(:user)
+      school.update!(creator_id: creator.id)
+      school.reject
+
+      expect { described_class.find_for_user!(creator) }.to raise_error(ActiveRecord::RecordNotFound)
+    end
   end
 
   describe '#verified?' do