## Why?
I'm about to change the functionality to allow user invitations to still work when the user already belongs to another participant. I'm doing this refactoring to make it easier for me to add that functionality as well as make it easier to be reviewed.

## What?
- Rename a function to avoid confusion with an upcoming function to send an invite to an existing user
- Split out the handler for inviting a new participant/user to participantsUsers
- Break down the handler for creating a new participant

We only have the one keycloak user role, so extracted into it's own method and constant, so we have less magic strings.

My alt+shift+O command removed them. Saving the file added them back