invoices: Use the same base method to export invoices and requests.

This fixes an inconsistency where the 'expiration' field was
relative for invoices, and absolute timestamp for requests.

This in turn fixes QML the timer refreshing the request list.

In order to prevent any API using that field from being silently
broken, the 'expiration' field is renamed as 'expiry'.

electrum/invoices.py

@@ -6,7 +6,7 @@ import attr
 
 from .json_db import StoredObject
 from .i18n import _
-from .util import age, InvoiceError
+from .util import age, InvoiceError, format_satoshis
 from .lnutil import hex_to_bytes
 from .lnaddr import lndecode, LnAddr
 from . import constants
@@ -222,6 +222,23 @@ class BaseInvoice(StoredObject):
         else:  # on-chain
             return get_id_from_onchain_outputs(outputs=self.get_outputs(), timestamp=self.time)
 
+    def as_dict(self, status):
+        d = {
+            'is_lightning': self.is_lightning(),
+            'amount_BTC': format_satoshis(self.get_amount_sat()),
+            'message': self.message,
+            'timestamp': self.get_time(),
+            'expiry': self.exp,
+            'status': status,
+            'status_str': self.get_status_str(status),
+            'id': self.get_id(),
+            'amount_sat': int(self.get_amount_sat()),
+        }
+        if self.is_lightning():
+            d['amount_msat'] = self.get_amount_msat()
+        return d
+
+
 @attr.s
 class Invoice(BaseInvoice):
     lightning_invoice = attr.ib(type=str, kw_only=True)  # type: Optional[str]