feat: add 'extra' column to saved_queries GET (#13662)
feat: add 'extra' column to saved_queries GET (#13662)

This column contains schedule information when the feature flag
`SCHEDULED_QUERIES` is enabled. Adding it here makes it available
through the REST API.
airbnb/caravel,apache/incubator-superset,mistercrunch/panoramix,mistercrunch/panoramix,airbnb/caravel,apache/incubator-superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,mistercrunch/panoramix,apache/incubator-superset,airbnb/caravel,airbnb/caravel,apache/incubator-superset,mistercrunch/panoramix,apache/incubator-superset,zhouyao1994/incubator-superset