Rename in documentation Permission to UserPermission

### Overview

Clarify the purpose of UserPermission (previously Permission) in document and code.

### Reason for change
When it was just called Permissions it was hard to remember its name - permissions is ambiguous.

### Action Items
Rename everywhere that it appears
- [ ] table spreadsheet
- [ ] ERD
- [ ] review any issues with "permission" in them to see if they need to be updated or at least put a note in the issue, indicating the change

### Resources/Instructions
- [ ] [Issues with the word permission in them](https://github.com/hackforla/peopledepot/issues?q=is%3Aissue+is%3Aopen+permission)
- [ ] #22 definitely
- [ ] #148 definitely
- [ ] #150 - possibly
- [ ] [table spreadsheet](https://docs.google.com/spreadsheets/d/1x_zZ8JLS2hO-zG0jUocOJmX16jh-DF5dccrd_OEGNZ0/edit?gid=990760269#gid=990760269)
- [ ] [ERD](https://lucid.app/lucidchart/ac2f3e81-00d2-4257-b1fc-266d7f0a4cbe/view?page=0_0#)