Add params to allow possibility to make group by on queries

[geoffreyaldebert]

We want to be able to do query like that :

SELECT COLUMN1, SUM(COLUMN2) FROM TABLE  GROUP BY COLUMN1 LIMIT 10;
SELECT COLUMN1, AVG(COLUMN2) FROM TABLE  GROUP BY COLUMN1 LIMIT 10;
SELECT COLUMN1, COUNT(COLUMN2) FROM TABLE  GROUP BY COLUMN1 LIMIT 10;
SELECT COLUMN1, COUNT(COLUMN2) FROM TABLE  GROUP BY COLUMN1 LIMIT 10;
SELECT COLUMN1, MIN(COLUMN2) FROM TABLE  GROUP BY COLUMN1 LIMIT 10;
SELECT COLUMN1, MAX(COLUMN2) FROM TABLE  GROUP BY COLUMN1 LIMIT 10;

maybe implemented like that :

https://tabular-api.data.gouv.fr/api/resources/<resource_id>/data/?groupby_x=column1&groupby_y=column2&operator=sum&limit=100

maybe limit the limit size