RFC: Add a Prism native manifest based modpack export/import format

Goal

The ability to export/import a Prism modpack in a Prism native format that references mods from their original providers rather than bundling the mod files themselves, in order to enable easy sharing and updating of multi-provider modpacks without relying on Curseforge or Modrinth hosting.

Motivation

I make a modpack every year for the boys annual minecraft playthrough, and sharing/updating packs can be such a hassle.

Historically I'd use Prism to create the modpack, export as a Curseforge .zip, and host it on the Curseforge platform. The annoyance here is that making an update to the modpack means having to wait for Curseforge approval (if it ever even does get approved), which is annoying when you're changing configs and adding a mod or two potentially multiple times per day as you go.

Additionally, some mods are hosted exclusively on either Curseforge or Modrinth. While Modrinth just doesn't allow Curseforge mods, including Modrinth mod jars in the Curseforge export significantly increases their review/approval time (and sometimes fails review if its a smaller mod that's not on their list). It also the makes the .zip file too big to send over a messaging platform like Discord, if you're doing that instead of hosting on Curseforge/Modrinth.

Specification

I suggest adding an extra export/import option in a Prism-native modpack format, separate to the current Prism instance import/export. It could be something as simple as exporting files you select (i.e. config and defaultoptions), in addition to a prism-pack.json (or any text format) that describes mods and basic properties, into a .zip file.

prism-pack.json could be something like:

{
	"manifestVersion": 1,
	"instance": {
		"name": "My Modpack",
		"version": "1.2.1",
		"minecraft": "1.21.1",
		"loader": {
			"type": "neoforge",
			"version": "47.1.106"
		}
	},
	"mods": [
		{
		  "provider": "modrinth",
		  "projectId": "sodium",
		  "versionId": "abc123"
		},
		{
		  "provider": "curseforge",
		  "projectId": "123456",
		  "fileId": "654321"
		}
	]
}

Why this is useful:

• Smaller filesize makes sharing packs with people much easier
• Allows sharing packs with mods that are exclusive to either Modrinth or Curseforge
• Prism already allows updating a Curseforge modpack from url/file, which should be easy to extend to a Prism-native solution
• Prism doesn't have to host anything themselves, and enables self-hosted modpack distribution methods independent of Modrinth/Curseforge -I can uninstall Curseforge/Overwolf finally

Drawbacks

• Requires introducing a maintaining a new modpack format, alongside the Curseforge and Modrinth formats.
• Remote manifests and self-hosted modpacks can be a security concern, as they're not vetted like Curseforge/Modrinth packs are. Though this should be minimal if no "override" files are provided, since mods are still hosted on those platforms, perhaps a warning not to trust strangers should be displayed when using this feature regardless.

Unresolved Questions

• How many people create their own packs to play with a couple friends/family? I've seen a lot around, but that could be selection bias. Is it enough to warrant implementing this feature?

Alternatives Considered

https://github.com/PrismLauncher/PrismLauncher/issues/4378: This solves most of the problems I have, but still doesn't allow easy sharing of packs that are based on one platform but contain mods from the other, due to file size concerns (that issue only mentions linking Modrinth, Curseforge or full exported .zip files). However, would be easier to implement I suspect, and removes the need for maintaining another modpack format. I would be very satisfied to see that implemented instead, and just not use Modrinth exclusive mods to avoid the hassle.

This suggestion is unique

• I have searched the issue tracker and did not find an issue describing my suggestion, especially not one that has been rejected.

You may use the editor below to elaborate further.

Potential alternatives I've tried:

• Packwiz - Has the same filesize issue with exporting in a Curseforge pack format with Modrinth/external mods (included as .jar). A lot less usable for people not accustomed to CLI applications, which I would argue a good chunk of casual modpack creators aren't.
• Moddermore - Misses a lot of nice features that Prism has like automatically including mod dependencies. I could update the pack on Prism and then copy those changes over to Moddermore, but it doesn't allow updating a list with a Prism export, so I'd have to find all the new mods and add them manually. Also, it doesn't allow sharing mod config files, and Prism doesn't let you update a custom pack (i.e. not Modrinth/Curseforge hosted) by file/URL, as far as I am aware, so you'd have to make a new instance and copy over your saves/options files (trust me this can be a nightmare with some people).

As a side note, the feature could also be combined with the idea in https://github.com/PrismLauncher/PrismLauncher/issues/4378, where we can self-host our new exported Prism modpack file (or a version manifest referencing versions of modpacks in any format) to allow auto updates by URL, removing the need to share .zip files altogether. In this case you can have the Prism-native modpack export simply be a manifest.json as above, but with an optional added URL to download configs/overrides etc, something like:

"overrides": {
	"url": "https://github.com/me/my-modpack/releases/download/1.2.1/configs.zip",
	"sha256": "..."
}

That would make modpacks completely self hostable, and just as easy to make and update as Curseforge/Modrinth packs, but without the platform specific limitations and with the other great features Prism has.

Just mentioning as a cool idea that would compliment this feature, doesn't have to be in scope of this RFC.