(Re-)allow task help dict to contain unused keys #793
Description
Previously it has been possible to define dictionary with docstring for each argument used in a file, then pass same dict in
@task(help=help_dict) to all tasks with parameters that have same meaning.
This made it possible to document each parameter only once in a single place, rather then document same parameters repeatedly for each task.
This is helpful especially in cases where most tasks in a file do actions based around same concepts.
After #611 this seems no longer possible, as any task that doesn't use all arguments defined in the help_dict will throw an error.
For example if one has tasks add_album(artist_id, album_id), find_albums(artist_id), find_artist(album_id) where previously something like:
help_dict = {
"artist_id": "Identifier for artist or band",
"album_id": "Identifier for the album (UUIDv4)"
}could be used to all tasks, now find_albums and find_artist tasks would cause error, since the tasks don't define one of the parameters listed in help_dict.
