Messagable::threads() does not respect soft deletes - so how do I truly remove a participant?

[cmgmyr]

Discussed in #376

^{Originally posted by cyrillkalita December 26, 2021}
Could be a silly question, really, but BelongsToMany does not account for SoftDeletes.

So a test structured like this, fails:

• create a thread,
• add a user participant to a thread
• remove user participant using removeParticipant()

The pivot attribute deleted_at is populated, as expected.
so:

1. thread->participants()-count() is 0, as expected, but
2. $user->threads()->count() still returns 1, because this is how BelongsToMany works

I read #205 and cannot help but wonder: am I missing something obvious?