Modular Middleware Layer (Processing Transactions Before They Reach the Destination)

I would like to propose a feature for Lunch Flow that introduces a middleware layer between transaction ingestion and delivery to the destination


What is Middleware in this context?

Instead of sending transactions directly from a source to a destination, transactions would pass through a configurable pipeline of processing steps (middlewares). Each middleware can inspect and modify the transaction before it is delivered to the destination.


Why this is useful
A middleware layer would enable a modular approach to adding new functionality to Lunch Flow without increasing complexity for the end user.

Instead of every feature requiring core code changes, features can be introduced as independent middleware modules. This fits well with Lunch Flow's existing design philosophy: simple and easy to use by default, while still supporting advanced customization when needed.

A middleware structure would allow:

• core middleware layers created and maintained directly within Lunch Flow, enabling more advanced functionality over time, and

• the option for users to write their own middleware layers when dealing with specialized or edge-case scenarios.

Any additional processing, whether cleanup, deduplication, rule execution, or enrichment happens inside the middleware pipeline. The result is flexibility without added complexity.

Requirements / Expectations

1. Modular and opt-in
   Users should be able to enable only the middlewares they need.
   

2. Execution order control
   Users should be able to reorder the middlewares in the pipeline.
   

3. Open for external integrations
   Ideally expose a middleware API so users can build their own modules.
   

4. Middleware modifies the transaction before it reaches the destination
   The destination should only receive the final, processed version.