Epic: Check in bug tracker and resolution

### Overview
Associated check in bug issues:
- [ ] #1411
- [ ] #1795
- [ ] #1530

Current overview of Check In Bug per @trillium:

**Overview:**
- We have accurate timestamps for when the event should start, but the timestamp's date creation is happening sometimes on the day before because of timezone differences between Pacific Time and GMT.
- So, we need to update the backend function to take into account timezone differences of the base timestamp vs. now.

**Here's a summary of what happens with events on VRMS:**
- A recurring event is generated or updated
- The front end sends a timestamp with the user's selected time to the backend
- The backend stores that timestamp in GMT
- Periodically (weekly) the backend runs a script checking to see if any events happen on a day of the week (e.g., Thursday).
- Within this bucket of events, a new date is generated in today's time and then the hour of that now current timestamp is set to the same hour as the stored recurring event hour.
- Come check in time, a separate script is run to see if any of the events should be considered open (I believe the window is 30 min before start time and 30 min after the end of the event).
- If the event's date is off, due to it being created in the wrong timezone (e.g., GMT vs. PST), then when the hour is assigned, the time is roughly off by 1 day or +/- 1 hour.

### Action Items
Need to employ test-driven development to resolve this issue.
- [x] #1839
- [x] _(Pending research outcomes from #1839, additional issues will be added here)._ Where possible, portions of the create recurring events structure should be refactored into smaller functions so that they are more easily testable via unit tests.
- [x] https://github.com/hackforla/VRMS/issues/1872

**Now that a PR has been submitted/merged and the issue has been addressed in issue #1872, we will plan on:**
- [ ] Rebuilding DEV with the latest fix
- [ ] Testing on Dev and checking the logs to confirm events are available for check-in on time
- [ ] Rebuilding PROD with changes from DEV
- [ ] Testing on PROD and checking the logs to confirm events are available for check-in on time.
- [ ] Close all of the remaining open issues in this epic after testing & confirming the fix.

### Resources/Instructions