Cal.com busy-times can silently return empty results

GET /v2/calendars/busy-times needs calendarsToLoad[i][credentialId] and [externalId], which come from GET /v2/calendars. A hand-built query string with raw brackets and a same-day dateFrom/dateTo returned success-looking output with 0 blocks. curl -s -G --data-urlencode for each param with a wider date range returned 24 real blocks. Either the encoding or the range could have been the cause, as both changed together. Don't read 0 blocks as 'free' until a wider, url-encoded query confirms it. Blocks are not labelled with event names, so this tells you only busy or free.