[Enhancement]: Support for merging authors with multiple pen names

[cassieesposito]

Describe the feature/enhancement

Some authors publish under multiple names. Currently, if I want all books by such an author to appear in the same list, I need to choose one pen name and assign all books they've written to that author. This is not ideal for at least two reasons:

• It's a bad metadata practice. Books should have the author listed in metadata as published.
• It hinders searchability. If I chose "Samuel Clemens" and you searched for "Mark Twain," You wouldn't find anything he'd written, even if I have his complete works.

[nichwall]

You can add multiple authors to a book, so in the meantime you could add "Samuel Clemens" to all books by him, and then also add "Mark Twain" to the appropriate books.

[advplyr]

Duplicate of https://github.com/advplyr/audiobookshelf/issues/908