= New Features

* The timed_queue and sharded_timed_queue connection pools (the
  default on Ruby 3.2+) now implement a num_waiting method, which will
  return now many threads or fibers are waiting to checkout a
  connection. This can be used for metrics on how loaded the
  connection pool is, which can help provide information on whether
  the connection pool max size should be modified.

* A class_table_inheritance_constraint_validations plugin has been
  added, which will allow subclasses using the class_table_inheritance
  plugin to respect constraint validations for all of the class's
  tables.

* On PostgreSQL 18+, primary key and unique constraints now support a
  :without_overlaps option to use WITHOUT OVERLAPS, turning the
  constraint into an exclusion constraint on the last column.

* On PostgreSQL 18+, foreign keys now support a :period option to use
  PERIOD, which makes it so the final column in the constraint must be
  covered in the referenced table (potentially covered by a
  combination of rows).

* On PostgreSQL 15+, unique constraints now support a
  :nulls_not_distinct option, to use NULLS NOT DISTINCT, which will
  treat NULL values as separate values when determining uniqueness.

* On PostgreSQL 11+, primary key, unique, and exclude constraints now
  support an :include option to used INCLUDE, which includes
  additional columns in the related index, to increase opportunities
  for index-only scans.

* On PostgreSQL 9.2+, check constraints now support a :no_inherit
  option to prevent inheritance of the constraint.

* In addition to null: false to specify NOT NULL for columns, you can
  now specify not_null: true, and you can use a hash value for the
  :not_null option to provide constraint-specific options. On
  PostgreSQL 18+, you can provide a :name option inside the hash to
  name the related NOT NULL constraint, which allows for altering the
  constraint and dropping the constraint by name. You can also provide
  the :no_inherit option in the hash to prevent inheritance of the
  constraint.
