Create new volunteer and organizer roles limited to check-ins only

[samderanova]

To start off the construction of our check-in process, we'll have to create new volunteer and organizer roles to grant them access to only the check-in page on the admin site.

While there is a tech_organizer role currently in use, it is not being used, so this can simply be replaced by the organizer role. Additionally, the volunteer role already exists, so the only role that really needs to be created is the organizer one.

[taesungh]

We already have the volunteer role in the API but will need an organizer role. We can also create a new ORGANIZER_ROLES, similar to ADMIN_ROLES which includes what we need from #268.

On the Admin site side, we should repurpose adminRole.ts as authorization.ts for various Admin-related authorizations.

• Update isAdminRole to allow organizer and volunteer
• Use separate isApplicationManager function for the previous admin roles (director and reviewer).
• Create an empty page called Participants for [Admin Site] Create separate page to facilitate participant check-in process #269 and show this in the AdminSidebar
• Hide the Applicants path and restrict the related pages to roles which satisfy isApplicationManager
  • Could just redirect to Admin dashboard if unauthorized cause layout itself will check general isAdminRole

[taesungh]

Update: volunteers will not be assigned check-in duty, so we'll need to remove them. Will include as part of #326.