Log Message:
databases/ruby-sequel: update to 5.20.0

=== 5.20.0 (2019-05-01)

* Fix reversing of alter_table add_foreign_key when :type option is used \ 
(jeremyevans) (#1615)

* Switch from using instance_exec to define_method for model associations and in \ 
some plugins (jeremyevans)

* Fix Database#server_version when using mysql2 adapter with mysql driver on \ 
MariaDB 10+ database (v-kolesnikov) (#1614)

* Make one_to_one setter method handle models that use joined datasets \ 
(jeremyevans) (#1612)

* Make auto_validations plugin work with the class_table_inheritance plugin \ 
(jeremyevans) (#1611)

* Avoid use of instance_exec for PlaceholderLiteralString#with_dataset (jeremyevans)

* Recognize float unsigned database types as float (keeguon, jeremyevans) (#1609)

* Support :savepoint options to Database#{after_commit,after_rollback} for \ 
making the hooks handle savepoints (jeremyevans)

* Avoid use of instance_exec in association_dependencies plugin (jeremyevans)

* Add pg_auto_constraint_validation_override to the \ 
pg_auto_constraint_validations plugin, for customizing columns and error message \ 
per constraint (jeremyevans)

* Make Database#check_constraints on PostgreSQL also include constraints where \ 
the related columns are not known (jeremyevans)