Single-record relationships

agent.customizeCollection('towns', collection =>
  collection.addManyToOneRelation('country', 'countries', {
    foreignKey: 'country_id',
    foreignKeyTarget: 'id', // Optional (uses `country` primary key by default)
  }),
);

ForestAdmin.customize do
  customize_collection('towns') do |collection|
    collection.add_many_to_one_relation('country', 'countries',
      foreign_key: 'country_id',
      foreign_key_target: 'id' # Optional (uses `country` primary key by default)
    )
  end
end

// Configure one side of the relationship ...
agent.customizeCollection('mayors', collection => {
  collection.addOneToOneRelation('city', 'cities', {
    originKey: 'mayor_id',
    originKeyTarget: 'id', // Optional (uses `mayors` primary key by default)
  });
});

// ... and the other one.
agent.customizeCollection('cities', collection => {
  // ⚠️ Not 'OneToOne'
  collection.addManyToOneRelation('mayor', 'mayors', {
    foreignKey: 'mayor_id',
    foreignKeyTarget: 'id', // Optional (uses `mayors` primary key by default)
  });
});

ForestAdmin.customize do
  # Configure one side of the relationship ...
  customize_collection('mayors') do |collection|
    collection.add_one_to_one_relation('city', 'cities',
      origin_key: 'mayor_id',
      origin_key_target: 'id' # Optional (uses `mayors` primary key by default)
    )
  end

  # ... and the other one.
  customize_collection('cities') do |collection|
    # ⚠️ Not 'one_to_one'
    collection.add_many_to_one_relation('mayor', 'mayors',
      foreign_key: 'mayor_id',
      foreign_key_target: 'id' # Optional (uses `mayors` primary key by default)
    )
  end
end