Create Table: Event Occurrence

### Overview

We need to create the EventOccurrence table so that we can update a shared data store across hackforla.org, vrms, civictechjobs, and tables (onboarding) project.

#### Details
A table and a model are the same thing

### Action Items
- [ ] Identify and document (below) what other tables are associated (see ERD under Resources)
- [ ] Create a single model in Django (defining schema)
- [ ] Write a test for the relationships this model will have with other models (e.g., creating a user and assigning them a set of permissions on a project).
- [ ] Write an API end point
- [ ] Write API unit tests
- [ ] Document the endpoint in Redocs

### Resources/Instructions
- See [People Depot Resources wiki page](https://github.com/hackforla/peopledepot/wiki/Resources-and-Links) for links
- ERD
- Spreadsheet: [PD: Table and field explanations, Current Field Permission tab](https://docs.google.com/spreadsheets/d/1x_zZ8JLS2hO-zG0jUocOJmX16jh-DF5dccrd_OEGNZ0/edit?gid=749942651)
- API Endpoint
- See [this Wiki page](https://github.com/hackforla/peopledepot/wiki/Create-Table-issues-data-gathering-workflow) for instructions on the data-gathering workflow for Create Table issues
- [ADD ANY OTHER RESOURCES/INSTRUCTIONS]

### Items to document (referenced above)

- [ADD ITEMS TO DOCUMENT]

#### Description

- Individual event that's generated from the associated potentially recurring parent event object.
- Future event occurrences need to be regenerated if the parent event's timing changes. If the `start_time` of the new occurrence matches an old one, any changes from the old occurrence will be transferred to the new occurrence before the old one is deleted.

### Data Fields

- [ ] Copied from spreadsheet and confirmed according to ERD

| Name | Type | FK Table | FK Table Issue(s) | comments |
| ---- | ---- | -------- | ----------------- | - |
| event | UUID | event | #14 #173 | reference to parent event object |
| start_time | DateTimeField | | | generated from event |
| changes | UUID | eventoccurancechange | #614 | fields that are user-modified and different from the parent event's fields. |

### FK status
- #14
- #173
- #614

#### Swagger Endpoint Link

- [ADD SWAGGER ENDPOINT LINK]