feat: Add minimum affinity filter to affinity result grouping

- Introduced a `min_affinity` parameter to the `affinity_result_by_tracking` function, allowing users to specify a threshold for filtering affinity results.
- Updated the logic to skip results with affinities below the specified minimum, enhancing the relevance of grouped detections.
- Improved function documentation to include details about the new parameter and its purpose.

playground.py

@@ -1197,13 +1197,22 @@ display(affinities)
 # %%
 def affinity_result_by_tracking(
     results: Iterable[AffinityResult],
+    min_affinity: float = 0.0,
 ) -> dict[TrackingID, list[Detection]]:
     """
     Group affinity results by target ID.
+
+    Args:
+        results: the affinity results to group
+        min_affinity: the minimum affinity to consider
+    Returns:
+        a dictionary mapping tracking IDs to a list of detections
     """
     res: dict[TrackingID, list[Detection]] = defaultdict(list)
     for affinity_result in results:
-        for _affinity, t, d in affinity_result.tracking_association():
+        for affinity, t, d in affinity_result.tracking_association():
+            if affinity < min_affinity:
+                continue
             res[t.id].append(d)
     return res