Add docs for error code
Add moving new tasks into the default bucket when none was provided
Add moving tasks in default bucket when deleting one
Fix tests again
Add test for removing a bucket
Fix tests
Prevent removing the last bucket
Remove the empty pseudo bucket
Add migration to create a new bucket for each list (and put all tasks in it
Co-authored-by: kolaente <k@knt.li>
Reviewed-on: vikunja/api#446
