* [SIP-5] Open a new /api/v1/query endpoint that takes query_obj
- Introduce a new handle_superset_exception decorator to avoid repeating the logic for catching SupersetExceptions
- Create a query_obj_backfill method that takes form_data and constructs a query_obj that will be constructed in the client in the future. Use the backfill in explore_json.
- Create a new /api/v1/query endpoint that takes query_obj only and returns the payload data. Note the query_obj is constructed in the client. The endpoint currently only handles query_obj for table view viz (we'll be adding support to new viz types as we go).
- Unit test to verify the new endpoint for table view
* fix tests and lint errors
* - Move the new query endpoint into its own api.py view.
- Create QueryObject and QueryContext class to encapsulate query_object to be built from the client and additional info (e.g. datasource) needed to get the data payload for a given query
- Remove the query_obj_backfill as we'll start building the first query_object on the client so it no longer makes sense to have a short-lived backfill for the matter of days.
* Fixing lint and test errors
* Fixing additional lint error from the previous rebase.
* fixing additional lint error
* addressing additional pr comments
* Make /query accept a list of queries in the query_context object.
* fixing a lint error
* - Move time_shift based calculation and since, until check into util
- Add typing info for get_since_until
- Add new unit tests to verify time_shift calculation and the since until check
