Add Rake task to GDPR delete users

lib/tasks/gdpr_delete.rake

@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+namespace :gdpr do
+  desc 'Deletes user accounts in accordance with GDPR. ' \
+       'Requires a text file with external user IDs (one per line) and ' \
+       'the corresponding consumer for deletion. Pass those via ' \
+       'TXT=/path/to/file.txt and CONSUMER=Name.'
+  task delete_users: :environment do
+    text_file_location = ENV.fetch('TXT')
+    consumer_name = ENV.fetch('CONSUMER')
+
+    if text_file_location.blank? || consumer_name.blank?
+      warn '--------------------------------------'
+      warn 'GDPR deletion tool to remove personal user data. USAGE:'
+      warn '--------------------------------------'
+      warn 'rake gdpr:delete_users TXT=./accounts.txt CONSUMER=openHPI'
+      exit 1
+    end
+
+    consumer = Consumer.where('lower(name) = ?', consumer_name.downcase).first
+
+    if consumer.blank?
+      warn '--------------------------------------'
+      warn "ERROR: The consumer '#{consumer_name}' was not found but is mandatory."
+      warn '--------------------------------------'
+      exit 2
+    end
+
+    user_ids = begin
+      File.readlines(text_file_location).map(&:strip).compact_blank
+    rescue SystemCallError => e
+      warn '--------------------------------------'
+      warn "ERROR: The file '#{text_file_location}' could not be opened: #{e.message}"
+      warn '--------------------------------------'
+      exit 3
+    end
+
+    unknown_user_ids = []
+    errored_user_ids = []
+    users_deleted = 0
+
+    user_ids.each do |user_id|
+      user = ExternalUser.find_by(external_id: user_id, consumer:)
+      if user.blank?
+        unknown_user_ids << user_id
+        next
+      end
+
+      if user.update(name: 'Deleted User', email: nil)
+        users_deleted += 1
+      else
+        errored_user_ids << user_id
+      end
+    end
+
+    if unknown_user_ids.any?
+      warn '--------------------------------------'
+      warn 'WARNING: Some user IDs were not found:'
+      warn '--------------------------------------'
+      unknown_user_ids.each do |user_id|
+        warn user_id
+      end
+    end
+
+    if errored_user_ids.any?
+      warn '--------------------------------------'
+      warn 'WARNING: Some user IDs were found but were not processed successfully:'
+      warn '--------------------------------------'
+      errored_user_ids.each do |user_id|
+        warn user_id
+      end
+    end
+
+    puts '--------------------------------------'
+    puts "SUCCESS: #{users_deleted} user(s) deleted."
+    puts '--------------------------------------'
+  end
+end