Add funding related rest endpoints, refactor pre-existent rest endpoints to use get_ prefix. Add function to calculate flags easily. Add example test to create a funding offer.

examples/rest/create_funding_offer.py

@@ -0,0 +1,26 @@
+import os
+
+from bfxapi.client import Client, Constants
+from bfxapi.utils.flags import calculate_offer_flags
+from bfxapi.rest.typings import List, FundingOffer, Notification
+
+bfx = Client(
+    REST_HOST=Constants.REST_HOST,
+    API_KEY=os.getenv("BFX_API_KEY"),
+    API_SECRET=os.getenv("BFX_API_SECRET")
+)
+
+notification: Notification = bfx.rest.auth.submit_funding_offer(
+    type="LIMIT", 
+    symbol="fUSD", 
+    amount="123.45", 
+    rate="0.001", 
+    period=2, 
+    flags=calculate_offer_flags(hidden=True)
+)
+
+print("Offer notification:", notification)
+
+offers: List[FundingOffer] = bfx.rest.auth.get_active_funding_offers()
+
+print("Offers:", offers)