#'org-time-stamp prompts a minibuffer that reads control strings from the user, and call
#'org-insert-time-stamp to insert the resulting time stamp as a string into the buffer. For example, the control string
"2021-01-01 9am" results to the time stamp
"<2021-01-01 Fri 09:00>".
How to factor these functions to create a new function that still prompts a minibuffer, but only returns a string without insertion? Some thing like
(org-time-stamp-read "2021-01-01 9am") ;; => "<2021-01-01 Fri 09:00>"