Send reminders one by one in Timely Cloud Function 【Merged】

[alidezhihui]

The implementation right now is sending all the reminders in one response. It can be a problem because if there is an error raised due to one reminder, all the other reminders will not be updated or dispatched: the reminder handler () stopped working.

New Design:

• send them one by one in parallel.

[alidezhihui]

next step: merge it