make db.py context manager operate in a transaction.

lnbits/db.py

@@ -15,22 +15,26 @@ class Database:
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
+        self.connection.commit()
         self.cursor.close()
         self.connection.close()
 
     def fetchall(self, query: str, values: tuple = ()) -> list:
         """Given a query, return cursor.fetchall() rows."""
-        self.cursor.execute(query, values)
+        self.execute(query, values)
         return self.cursor.fetchall()
 
     def fetchone(self, query: str, values: tuple = ()):
-        self.cursor.execute(query, values)
+        self.execute(query, values)
         return self.cursor.fetchone()
 
     def execute(self, query: str, values: tuple = ()) -> None:
         """Given a query, cursor.execute() it."""
-        self.cursor.execute(query, values)
-        self.connection.commit()
+        try:
+            self.cursor.execute(query, values)
+        except sqlite3.Error as exc:
+            self.connection.rollback()
+            raise exc
 
 
 def open_db(db_name: str = "database") -> Database: