Application login for Guest Posting

### Problem I have

CoSocial.ca has been considering how to work engaging membership, and are considering inviting different folks to guest post from a specific account.

Currently the only supported login seems to be for users via OAuth.

### Solution I'd like

Ideally we could create application logins (client_id, client_secret, access_token) with specific scopes (excluding account modification), which we could then manually delete after the guest posting period.

### Alternatives considered

Sharing passwords 😬🙅

### Other

_No response_