FIX: Rename User#usernames that clashes with Group#name. (#6069)

app/jobs/scheduled/fix_user_usernames_and_groups_names_clash.rb

@@ -0,0 +1,29 @@
+module Jobs
+  class FixUserUsernamesAndGroupNamesClash < Jobs::Scheduled
+    every 1.week
+
+    def execute(args)
+      User.joins("LEFT JOIN groups ON lower(groups.name) = users.username_lower")
+        .where("groups.id IS NOT NULL")
+        .find_each do |user|
+
+        suffix = 1
+        old_username = user.username
+
+        loop do
+          user.username = "#{old_username}#{suffix}"
+          suffix += 1
+          break if user.valid?
+        end
+
+        new_username = user.username
+        user.username = old_username
+
+        UsernameChanger.new(
+          user,
+          new_username
+        ).change(asynchronous: false)
+      end
+    end
+  end
+end

spec/jobs/fix_user_usernames_and_group_names_clash_spec.rb

@@ -0,0 +1,15 @@
+require 'rails_helper'
+
+RSpec.describe Jobs::FixUserUsernamesAndGroupNamesClash do
+  it 'update usernames of users that clashes with a group name' do
+    user = Fabricate(:user)
+    Fabricate(:user, username: 'test1')
+    group = Fabricate(:group, name: 'test')
+    user.update_columns(username: 'test', username_lower: 'test')
+
+    Jobs::FixUserUsernamesAndGroupNamesClash.new.execute({})
+
+    expect(user.reload.username).to eq('test2')
+    expect(group.reload.name).to eq('test')
+  end
+end