add readme on pattern resolution

Author: CarsonDavis

sde_collections/models/README_PATTERN_RESOLUTION.md

@@ -0,0 +1,78 @@
+# URL Pattern Application Strategies
+
+## Strategy 1: Exclusive Patterns
+
+Patterns have exclusive ownership of URLs they match. System prevents creation of overlapping patterns.
+
+Example:
+```
+Pattern A: */docs/*          # Matches 100 URLs
+Pattern B: */docs/api/*      # Rejected - overlaps with Pattern A
+Pattern C: */blog/*          # Accepted - no overlap
+```
+
+Benefits:
+- Clear ownership
+- Predictable effects
+- Simple conflict resolution
+- Easy to debug
+
+Drawbacks:
+- Less flexible
+- May require many specific patterns
+- May need pattern deletion/recreation to modify rules
+
+## Strategy 2: Smallest Set Priority
+
+Multiple patterns can match same URLs. Pattern affecting smallest URL set takes precedence.
+
+Example:
+```
+Pattern A: */docs/*          # Matches 100 URLs
+Pattern B: */docs/api/*      # Matches 20 URLs
+Pattern C: */docs/api/v2/*   # Matches 5 URLs
+
+For URL "/docs/api/v2/users":
+- All patterns match
+- Pattern C wins (5 URLs < 20 URLs < 100 URLs)
+```
+
+Benefits:
+- More flexible rule creation
+- Natural handling of specificity
+
+Drawbacks:
+- Complex precedence rules
+- Pattern effects can change as URL sets grow
+- Harder to predict/debug
+- Performance impact from URL set size calculations
+
+## Implementation Notes
+
+Strategy 1:
+```python
+def save(self, *args, **kwargs):
+    # Check for overlapping patterns
+    overlapping = self.get_matching_delta_urls().filter(
+        deltapatterns__isnull=False
+    ).exists()
+    if overlapping:
+        raise ValidationError("Pattern would overlap existing pattern")
+    super().save(*args, **kwargs)
+```
+
+Strategy 2:
+```python
+def apply(self):
+    matching_urls = self.get_matching_delta_urls()
+    my_url_count = matching_urls.count()
+
+    # Only apply if this pattern matches fewer URLs than other matching patterns
+    for url in matching_urls:
+        other_patterns_min_count = url.deltapatterns.annotate(
+            url_count=Count('delta_urls')
+        ).aggregate(Min('url_count'))['url_count__min'] or float('inf')
+
+        if my_url_count <= other_patterns_min_count:
+            self.apply_to_url(url)
+```