Add attribute to posting transaction to differentiate internal vs external origin

[lakani]

User Story

As a user of the posting transaction system, I want to have a new attribute in the posting transaction that differentiates whether the posting originated from an internal or external source. If the posting is internal, the attribute should also indicate which module generated it.

Motivation

This enhancement will help in scenarios where postings are imported that have already been posted on another system. By knowing the origin and the generating module, it will be easier to track, filter, and audit transactions.

Acceptance Criteria

• A new attribute is added to the posting transaction object to indicate whether the posting is internal or external.
• If internal, the attribute should specify the generating module (e.g., 'payments', 'inventory', etc.).
• Documentation is updated to explain the attribute and its possible values.
• The import process should leverage this attribute to handle already-posted transactions from other systems.

Benefits

• Improved auditability and traceability of postings.
• Simplifies integration and data import from external systems.
• Reduces risk of duplicate postings when importing.