Support multiple enclosures/attachments

[Eitot]

Some decisions have to be made to support this.

1. How to store additional enclosure/attachment URLs

• Use the "enclosures" column of the "messages" table and store multiple URLs, separated by a delimiter. This option would require no changes to the database, but it would not be backwards compatible.
• Add a new column to the "messages" table and migrate existing data, optionally keeping the "enclosures" column.
• Add a new table and link the "messages" table to it, , optionally keeping the "enclosures" column.

2. How to show the enclosures in the enclosure bar of the article viewer

• Show file icons/previews and links for each enclosure/attachment
• Change the enclosure bar so that it shows a pop-up menu instead, similar to Mail:
  

3. What to do with the "Enclosure URL" column in the article list

4. What to do with the `$ArticleEnclosureFilename$` and `$ArticleEnclosureLink$` tags in article styles

Any ideas?

[github-actions]

This issue hasn't been updated in a while so we're going to mark it as stale. stale issues will automatically be closed after 60 days of inactivity. If this issue is still affecting you, please update us on how it affects you, and we'll keep it open. We are sorry that we haven't been able to prioritize it yet. Thank you for your contributions.