Enhance AbstractRepository with Custom Query Scopes

[shmuel-torii]

This pull request introduces enhancement to the AbstractRepository class, empowering subclasses to add custom "scopes" to the repository's queries. The changes include the addition of a new method called startQueryBuilder, which can be overridden in subclasses to apply additional query constraints specific to their needs.

With this modification, subclasses can now override the startQueryBuilder method to add their own scopes, such as:

protected startQueryBuilder(queryBuilder: Knex): Knex.QueryBuilder {
  return queryBuilder(this.tableName).where('tenantId', 'xyz');
}

By overriding startQueryBuilder, subclasses can inject additional conditions into the query, tailored to their specific requirements. For example, the above implementation adds a scope that filters records based on a tenantId of 'xyz'.

Please review and merge this pull request if the changes align with the project's goals. These modifications provide greater flexibility and extensibility to the AbstractRepository class, allowing subclasses to introduce custom query scopes and enhance the functionality of the repository.