Describe the bug
I have ~35 .etherpad files from ~10 years ago. I don't know the exact version used back then (though perhaps @vladikoff may)

I just setup etherpad locally and am attempting to import them.

But I'm running into this assert(authorId != null); line which is failing the import with AssertionError [ERR_ASSERTION]: The expression evaluated to a falsy value

Honestly have no idea if it's just the one problem or.. it's a harbinger and there's a pile of backcompat issues behind this one.

I'm open to writing my own migration script to update these old .etherpad files to something modern etherpad-lite can handle.. but... before I embark on that I wanted to see if any maintainers here have any bright ideas or useful resources. :)

I'm using import from the Web UI, not API.

To Reproduce
Here's an example .etherpad file that repros: https://gist.github.com/paulirish/da70e566b3911c90f9a0d4aaf867b8e7

Maybe related:

• Include Author when Importing a Document · Issue #4504 · ether/etherpad-lite
• Plumb author ID, add new padDefaultContent hook by rhansen · PR #5423 [merged] · ether/etherpad-lite that introduced the author -> authorId change

    at async <anonymous> (/opt/etherpad-lite/src/node/hooks/express/importexport.ts:84:7)
    at async Object.exports.doImport (/opt/etherpad-lite/src/node/handler/ImportHandler.ts:255:28)
    at async doImport (/opt/etherpad-lite/src/node/handler/ImportHandler.ts:156:5)
    at async Object.exports.setPadRaw (/opt/etherpad-lite/src/node/utils/ImportEtherpad.ts:118:5)
    at Pad.check (/opt/etherpad-lite/src/node/db/Pad.ts:716:9)

[2024-12-03T12:20:57.911] [ERROR] ImportHandler - Internal error during import: AssertionError [ERR_ASSERTION]: The expression evaluated to a falsy value:
[2024-12-03T12:20:57.910] [WARN] ImportEtherpad - (pad importtest) unsupported attributes (try installing a plugin): underline

Server:

• Etherpad version: 2.2.6, git sha 0c68ddc
• OS: docker on synology dsm
• Is the server free of plugins: YES. no plugins at all. (Though apparently i'll need plugins to add support for list, strikethrough, underline, and start )