Add rake task to clean up stale patient locations after school moves

When a patient moves school, their old `PatientLocation` record should be
deleted if it's safe to do so. However, due to how `safe_to_destroy?` was
previously defined, old `PatientLocations` were retained if the patient
had any attendance records at that location, even from previous
academic years.

This caused patients to appear in sessions for multiple schools
simultaneously, even if they had moved before any sessions at their old
school took place, leading to potentially misleading communications.

The underlying issue was fixed in PR #5115 by scoping attendance_records
to the `PatientLocation`'s academic year. This rake task cleans up the
existing stale records that accumulated before that fix.

Jira-Issue: MAV-2540

Author: jhenderson

lib/tasks/patient_locations.rake

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+namespace :patient_locations do
+  desc "Remove stale patient locations from previous schools"
+  task cleanup_post_school_move: :environment do
+    dry_run = ENV.fetch("DRY_RUN", "true") == "true"
+
+    puts "Starting cleanup of stale patient locations from previous schools"
+    puts "DRY RUN MODE - No records will be destroyed" if dry_run
+
+    patients_with_multiple_locations =
+      Patient.where(
+        id:
+          PatientLocation
+            .where.not(location_id: Location.clinic)
+            .where(academic_year: AcademicYear.current)
+            .group(:patient_id)
+            .having("COUNT(*) > 1")
+            .select(:patient_id)
+      )
+
+    total = patients_with_multiple_locations.count
+    puts "Found #{total} patients with multiple locations"
+
+    progress_bar =
+      # rubocop:disable Rails/SaveBang
+      ProgressBar.create(
+        total:,
+        format: "%a %b\u{15E7}%i %p%% %t",
+        progress_mark: " ",
+        remainder_mark: "\u{FF65}"
+      )
+    # rubocop:enable Rails/SaveBang
+
+    safe_to_destroy_count = 0
+
+    patients_with_multiple_locations.find_each do |patient|
+      patient_locations_to_destroy =
+        patient
+          .patient_locations
+          .where(academic_year: AcademicYear.current)
+          .where.not(location_id: patient.school_id)
+
+      safe_to_destroy_count += patient_locations_to_destroy.count
+
+      patient_locations_to_destroy.destroy_all unless dry_run
+
+      progress_bar.increment
+    end
+
+    puts(
+      if dry_run
+        "Would destroy: #{safe_to_destroy_count}"
+      else
+        "Safely destroyed: #{safe_to_destroy_count}"
+      end
+    )
+  end
+end