fix uncaught user input processing in date util

[melange396]

An improperly formatted date causes an uninformative 500 error, and a useful message should instead be bubbled up to the user with a better error code.

This was brought to our attention by sentry, see: https://cmu-delphi.sentry.io/issues/4893721093/

One way to fix this: the offending date() constructor call that puked here (found in server/utils/dates.py:time_value_to_day()) can be wrapped to catch exceptions and then rethrow them as ValidationFailedexceptions. This is similar to what is done in other input processing methods in server/_params.py; those exceptions extend HTTPException which is handled and presented to the user gracefully by the web server.

We probbly also wanna do it with the similar Week() constructor call in time_value_to_week() as well, because i presume that will fail in an analogous way on unchecked/raw user input values.

[melange396]

Itll also be good practice to first add a test that fails for this, then do the fix, then make sure the test now passes

[dmytrotsko]

Itll also be good practice to first add a test that fails for this, then do the fix, then make sure the test now passes

Actually, we already have tests for utils/dates.py here.
We also have integration test for the /csv endpoint here.
Here are list of params that were provided by user:

start_day=2023-01-01
end_day=2024-18-01 <----- the wrong date format, probably user missmatched date format, because we have YY-MM-DD.
geo_type=county
signal=chng:smoothed_outpatient_cli