track fiat value of payments (#1789)

* save fiat_amounts on payment creation

* show fiat amount in frontend

* add lnbits_default_accounting_currency

* extract fiat calculation logic into service

* move all currency conversions to calc_fiat_amounts

move all conversion logic into create_invoice so extensions can benefit aswell

* show user-defined and wallet-defined currency in frontend

* remove sat from fiat units

* make bundle

* improve tests

* debug log

lnbits/core/migrations.py

@@ -319,3 +319,11 @@ async def m011_optimize_balances_view(db):
         GROUP BY wallet
     """
     )
+
+
+async def m012_add_currency_to_wallet(db):
+    await db.execute(
+        """
+        ALTER TABLE wallets ADD COLUMN currency TEXT
+        """
+    )