feat: add comprehensive BOALF and balancing mechanism support

- Add BOALF, BOD, PN, B1610, SettlementStackPair, AcceptedVolumes models
- Implement get_latest_acceptances() and get_acceptances_by_time() methods
- Add get_physical_notifications(), get_bid_offer_data(), get_actual_generation()
- Add get_settlement_stack() and get_bm_units_reference() methods
- Fix BOALF model to match actual API response structure
- All BOALF endpoints now working with proper type validation
- Export new models in __init__.py for easy access

BOALF endpoints tested and working:
- /balancing/acceptances/all/latest ✅
- /datasets/BOALF ✅
- /datasets/PN, /datasets/BOD, /datasets/B1610 ✅
- /balancing/settlement/stack/all/{bid|offer}/{date}/{period} ✅
- /reference/bmunits/all ✅

Author: BenjaminWatts

elexon_bmrs/__init__.py

@@ -30,6 +30,17 @@
     SystemPricesResponse,
     SystemFrequencyResponse,
     ImbalancePricesResponse,
+    # BOALF and Balancing Mechanism models
+    BOALF,
+    BOD,
+    PN,
+    B1610,
+    SettlementStackPair,
+    AcceptedVolumes,
+    BOALFResponse,
+    BODResponse,
+    PNResponse,
+    B1610Response,
 )
 # Import commonly used enums
 from elexon_bmrs.enums import (
@@ -82,6 +93,17 @@
     "SystemPricesResponse",
     "SystemFrequencyResponse",
     "ImbalancePricesResponse",
+    # BOALF and Balancing Mechanism models
+    "BOALF",
+    "BOD",
+    "PN",
+    "B1610",
+    "SettlementStackPair",
+    "AcceptedVolumes",
+    "BOALFResponse",
+    "BODResponse",
+    "PNResponse",
+    "B1610Response",
     # Commonly used enums
     "DatasetEnum",
     "PsrtypeEnum",