Specify default scope in verify_credentials

Certain Mastodon/Pleroma front ends call verify_credentials to get the
default scope of a new toot.

Currently, Pleroma hardcodes this value to "public".

This patch changes it to the user's default_scope value.
2 jobs for verify-credentials-default-scope in 4 minutes and 52 seconds (queued for 4 seconds)
latest
Status Job ID Name Coverage
  Lint
passed #7344
lint

00:02:07

 
  Test
passed #7345
unit-testing

00:02:44