doctrine schema.yml m:n

Person:
  columns:
    # columns go here
  relations:
    Towns:
      class: Town
      refClass: PersonTown
      local: person_id
      foreign: town_id
      foreignAlias: Persons

Town:
  columns:
    # columns go here

PersonTown:
  columns:
    person_id: { type: integer, primary: true }
    town_id:   { type: integer, primary: true }