covid_hosp_facility_lookup should warn/error for not implemented cases

[dsweber2]

Unsure if this exists as an issue already, but the call

covid_hosp_facility_lookup(state = "WY", city = "New York") %>% fetch_tbl()

silently just returns the state result. As more than one input is invalid, this should probably return an error/warning to that effect.

[dshemetov]

Related to the discussion here. If we commit to doing those checks in the server, then no need to do that here.