checkin endpoint design

[fyliu]

This is a WIP for now and needs to be refined later.

custom endpoint example

I want to add an example of custom endpoint that's not just api/<table_name>/

1. /api/users/:user_id/meetings/?by_time=now/checkin/

This could be a shortcut for the below steps

1. /api/meetings/?by_user_id=:user_id get meetings a user should attend. Choose a meeting id from the list that happens currently
2. /api/checkins/:user_id?by_meeting_id=:meeting_id to check in

Maybe this is not a well-thought-out example. I'll work on something better later. This should go into PD docs in the future.

I kind of envision a project lead being able to check in project members at meeting doing something like

1. /api/projects/?by_name=VRMS/meetings/?by_time=now/users/ to get the list of people that should be attending
2. /api/checkins/:user_id?by_meeting_id=:meeting_id to check in.

Again, it's a pretty rough example where it's unclear where some of the values came from.