Backfill school_id column

In the previous two commits we added a `school_id` column on
`patient_locations`. This commit adds a data migration to make sure it
is populated for existing rows.

Jira-Issue: MAV-7114
Jira-Issue: MAV-7113

Author: thomasleese

db/data/20260427125506_backfill_patient_location_school.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class BackfillPatientLocationSchool < ActiveRecord::Migration[8.1]
+  def up
+    execute <<-SQL
+      UPDATE patient_locations
+      SET school_id = location_id
+      WHERE school_id IS NULL
+    SQL
+  end
+
+  def down
+    # Nothing to do to revert this.
+  end
+end

db/data_schema.rb

@@ -1 +1 @@
-DataMigrate::Data.define(version: 2026_04_22_155320)
+DataMigrate::Data.define(version: 2026_04_27_125506)