phase5: add saved searches, watchlist, and authenticated htmx flows

apps/scouting/services/saved_searches.py

@@ -0,0 +1,38 @@
+from decimal import Decimal
+from urllib.parse import urlencode
+
+from apps.players.forms import PlayerSearchForm
+
+IGNORED_QUERY_KEYS = {"page", "csrfmiddlewaretoken"}
+
+
+def _serialize_value(value):
+    if value is None:
+        return None
+    if hasattr(value, "pk"):
+        return value.pk
+    if isinstance(value, Decimal):
+        return str(value)
+    return value
+
+
+def extract_filters_from_params(params):
+    payload = params.copy()
+    for key in IGNORED_QUERY_KEYS:
+        payload.pop(key, None)
+
+    form = PlayerSearchForm(payload)
+    if not form.is_valid():
+        return {}
+
+    result = {}
+    for key, value in form.cleaned_data.items():
+        serialized = _serialize_value(value)
+        if serialized in (None, ""):
+            continue
+        result[key] = serialized
+    return result
+
+
+def saved_search_to_querystring(filters: dict) -> str:
+    return urlencode(filters, doseq=True)