[scd] return proper http code for too big area search on the SCD subscriptions endpoint

[Shastick]

While writing a scenario for the uss_qualifier I ran into a situation where the DSS does not use the proper HTTP code when the requested are is too large for subscription queries in the SCD context.

As per specification, in this situation, we should receive a 413 code, and not the observed 500 one.

The location in the code was found through the following DSS logs:

2024-01-11T13:51:43.660Z	error	errors/errors.go:81	Error during unary server call	{"error_id": "E:7998749e-a7f4-4a2b-a39c-46d7dac2e222", "stacktrace": "Got an unexpected error\n --- at /app/pkg/scd/subscriptions_handler.go:443 (Server.QuerySubscriptions) ---\nCaused by: Error searching Subscriptions in repo\n --- at /app/pkg/scd/subscriptions_handler.go:414 (Server.QuerySubscriptions.func1) ---\nCaused by: Could not calculate spatial covering\n --- at /app/pkg/scd/store/cockroach/subscriptions.go:313 (repo.SearchSubscriptions) ---\nCaused by: Area is too large (510062190.739560km² > 2500.000000km²)\n --- at /app/pkg/geo/s2.go:177 (Covering) ---\nCaused by: Area too large\n --- at /app/pkg/geo/errors.go:31 (init) ---", "error": "Area too large", "code": 0}

The proposed fix solves the issue: when running against a local build of the DSS, I observed the proper HTTP code being returned when the requested search area was too big.

[BenjaminPelletier]

Awesome, thanks :)