CompositeMigration class

A migration that combines multiple migrations into one

Example:

final migrations = [
  CompositeMigration(
    version: 3,
    description: 'Add multiple columns',
    steps: [
      RawSqlMigration(
        version: 0, // ignored in composite
        description: 'Add age column',
        upSql: 'ALTER TABLE users ADD COLUMN age INTEGER;',
        downSql: 'ALTER TABLE users DROP COLUMN age;',
      ),
      RawSqlMigration(
        version: 0, // ignored in composite
        description: 'Add phone column',
        upSql: 'ALTER TABLE users ADD COLUMN phone VARCHAR(20);',
        downSql: 'ALTER TABLE users DROP COLUMN phone;',
      ),
    ],
  ),
];