# TASK 1.2: Implement PostgreSQL KDS Source Reader

## Summary

Implement the source reader that reads current simulator-generated KDS data from the shared PostgreSQL warehouse.

The reader treats PostgreSQL as the current simulator source only. It must not become the Redshift target abstraction.

## Dependencies

- TASK 1.1 (synthetic feed configuration and service contract)

## Files to Create

### 1. Source reader service

Create a source reader equivalent to:

- `ISyntheticKdsSourceReader`
- `SyntheticKdsSourceReader`

Exact names may differ.

The reader may use the existing `KDSContext` because PostgreSQL is the current source of simulator data.

### 2. Source read models

Create lightweight source DTO/read models if needed to decouple downstream mapping from EF-generated entities.

Recommended logical models:

- source order row
- source item row
- source item bump row
- source batch/snapshot result

## Files to Modify

### 3. Dependency injection registration

Register the source reader with the feed implementation.

## Required Behavior

The source reader must:

- read `kdsdev.orders` rows for a configured `store_guid`,
- read matching `kdsdev.items` rows for those orders,
- read matching `kdsdev.item_bumps` rows for those items,
- support full-refresh reads,
- support incremental reads when a checkpoint is provided,
- avoid reading unrelated stores,
- project only columns required by the phase-1 mapping,
- avoid loading the entire warehouse when a time/checkpoint boundary is provided.

Minimum source tables:

- `kdsdev.orders`
- `kdsdev.items`
- `kdsdev.item_bumps`

Optional:

- `kdsdev.condiments` remain out of scope because no phase-1 curated contract consumes them.

## Acceptance Criteria

- [x] Source reader can read orders by `store_guid`
- [x] Source reader can read items for selected orders
- [x] Source reader can read item bump state for selected items
- [x] Source reader projects only required columns
- [x] Source reader supports full-refresh source reads
- [x] Source reader supports an incremental boundary or leaves a clear extension point for TASK 2.2
- [x] Source reader is used only as source access, not Redshift target access
- [ ] No Redshift writes are implemented in this task
- [x] Solution builds without errors

## Notes

- Keep `KDSContext` as legacy/source access only.
- Do not remodel the whole PostgreSQL warehouse.
- Do not add payments, POS, inventory, or customer source reads.