class AlterMaxTeamSize
  def self.run
    improper_assignments = Assignment.all(:conditions => 'max_team_size = 0')
    improper_assignments.map do |assignment|
      assignment.max_team_size = 1
      assignment.save
    end
  end
end
Add script for changing max_team_size from 0 to 1
Add script for changing max_team_size from 0 to 1
