Delay to upgrade modpack

### Enhancement Type

Improve an existing feature

### Describe the enhancement

My server recently updated ATM8 to version 1.0.16, and there was a problem with the Hexerei mod in the pack where it reported version 0.3.1 on the client, but 0.3.0 is what is downloaded, and what the server expects.

Which had me thinking, what if we could set a delay after a release of a new update before the server applies that. Looks like today, they released 1.0.17 for ATM8. I havent updated yet, but I am guessing it fixes that issue, since it was released only a day later.

I don't know if the CURSEFORGE api gives info like when the file was uploaded or not. I was thinking something like `CF_UPGRADE_DELAY=2` would be a 2 day delay.

It's not a critical thing, just an idea I had when trying to troubleshoot the issue.

_edit_: Just upgraded to 1.0.17, and I still had that problem with Hexerei. I had to go on the server and copy the jar from my client to the server. There wasn't a version on there. So it seemed the client downloaded 0.3.0 version of hexerei but the server did not.

Start at the modpack upgrade startup path and investigate whether the CurseForge API exposes a file upload time. Define how CF_UPGRADE_DELAY=2 should affect newly released files, and verify that the server still selects compatible modpack files after the delay.

Written by the indexing model from the issue text.