Fix duplicate blank outputs during melt (#795)

* wip blank outputs

* wip: working

* store ids for promises correctly

* tests

* fix migraiton

* revert

* fix tests

* fix auth server

* fix last tests

* retroactively change migration, initial and m017_foreign_keys_proof_tables, remove c_b and replace with c_ (same for b_)

* fix constraint

* oops

* msg stack fix

* fix test foreign key constraint

* fix postgres tests

* foreign key constraint test

* should fix psql error

* foreign key constraint sqlite

* rename to update_blinded_message_signature

* drop outputs and change columns from melt_quotes table

* switch migration order

* reorder migrations again

* fix migration

* add tests

* fix postgres migration too

* create signed_at column postgres

* foreign key constraingt promises table

* migration tool

* readme

cashu/core/base.py

@@ -231,6 +231,10 @@ class BlindedMessage(BaseModel):
     id: str  # Keyset id
     B_: str  # Hex-encoded blinded message
 
+    @classmethod
+    def from_row(cls, row: RowMapping):
+        return cls(amount=row["amount"], B_=row["b_"], id=row["id"])
+
 
 class BlindedMessage_Deprecated(BaseModel):
     """
@@ -300,7 +304,7 @@ class MeltQuote(LedgerEvent):
     mint: Optional[str] = None
 
     @classmethod
-    def from_row(cls, row: Row):
+    def from_row(cls, row: Row, change: Optional[List[BlindedSignature]] = None):
         try:
             created_time = int(row["created_time"]) if row["created_time"] else None
             paid_time = int(row["paid_time"]) if row["paid_time"] else None
@@ -314,11 +318,6 @@ class MeltQuote(LedgerEvent):
 
         payment_preimage = row.get("payment_preimage") or row.get("proof")  # type: ignore
 
-        # parse change from row as json
-        change = None
-        if "change" in row.keys() and row["change"]:
-            change = json.loads(row["change"])
-
         outputs = None
         if "outputs" in row.keys() and row["outputs"]:
             outputs = json.loads(row["outputs"])