Partially-filter author field values that contain email addresses

[jayaddison]

Describe the bug
Rarely, the author field of a recipe may return a value that contains -- or is -- an email address.

That may be OK if it's what the recipe author intended (it seems reasonable for them to choose how to display their own authorship details), but I think it'd seem a little unusual for email addresses to appear -- without appearing as mailto: hyperlinks -- in the application's search results. I don't think we want to turn them into hyperlinks, because that'd seem like it's putting those authors on a different level of authority/appearance to other recipe authors. In addition: it'd be easier to filter our database backups for the presence of email addresses -- something we don't want to appear -- if we can filter out these rare existing cases.

Short-term I think that removing the @ and domain-part of each address may be sufficient; a username / inbox name is a form of name, and each recipe result includes a hyperlink to the recipe itself (which should usually be on the same domain.. perhaps a sign of something particularly odd if the author looks like an email and doesn't match the recipe domain -- but we haven't seen that so far).

To Reproduce
Steps to reproduce the behavior:

1. N/A (not including repro details here)

Expected behavior
Display the username part only from any email addresses found within the contents of the author field.

Screenshots
N/A (not including screenshots here)