This pull request implements the discussed changes in 2193.

Changes

• Set's the default generated clause to GENERATED BY DEFAULT to allow database seeding with the OOTB setup.
• Updates the PostgresAdapter insert statements to include OVERRIDING SYSTEM VALUE to allow inserting into columns that were created with the GENERATED ALWAYS clause. This allows database seeding.

How to set GENERATED ALWAYS

In your migration file add the option generated.

...

public function up()
{
    $this->table('my_table')
        ->addColumn('id', 'integer', [
            'autoIncrement' => true,
            'limit' => 11,
            'generated' => \Phinx\Db\Adapter\PostgresAdapter::GENERATED_ALWAYS,
          ])
          ...
}