Using "sortby":"category" results in an internal server error

This problem has been reported by a user in the ask-forum and can be reproduced via the playground:

Removing sortby or switching to distance makes the problem disappear.

This problem seems to have existed for a bit…

I think the problem is that the query used for requesting pois is

openpoiservice/openpoiservice/server/api/query_builder.py

Lines 76 to 79 in 0bc26a9

    
           bbox_query = db.session \ 
        
               .query(POIs) \ 
        
               .filter(*geom_filters) \ 
        
               .subquery()

which does not include any information about categories.
When defining what to sort by, however, it tries to use the category column from the query above, which does not exist:

openpoiservice/openpoiservice/server/api/query_builder.py

Line 89 in 0bc26a9

sortby_group.append(bbox_query.c.category)

I don't know how to fix this though…

Was fixed in #121.

	bbox_query = db.session \
	.query(POIs) \
	.filter(*geom_filters) \
	.subquery()