feat: make user agent customizable (#32506)

superset/db_engine_specs/bigquery.py

@@ -459,7 +459,7 @@ class BigQueryEngineSpec(BaseEngineSpec):  # pylint: disable=too-many-public-met
         :param sql: SQL query with possibly multiple statements
         :param source: Source of the query (eg, "sql_lab")
         """
-        extra = database.get_extra() or {}
+        extra = database.get_extra(source) or {}
         if not cls.get_allow_cost_estimate(extra):
             raise SupersetException("Database does not support cost estimation")
 
@@ -469,6 +469,7 @@ class BigQueryEngineSpec(BaseEngineSpec):  # pylint: disable=too-many-public-met
             database,
             catalog=catalog,
             schema=schema,
+            source=source,
         ) as engine:
             client = cls._get_client(engine, database)
             return [