GDLauncher Add Modrinth mod/modpack support

(This picks up where #1352 left off after the big history clean)

Purpose

Currently, GDLauncher does not support downloading mods/modpacks hosted on the Modrinth platform. This feature has been requested in issue #768.

I'm aware of GDevs' other project ferium which already supports Modrinth, and also the gdlib-refactor branch (which I assume may eventually succeed GDLauncher?), but that branch is far from completion.

Approach

This PR allows users to search for and install mods and modpacks hosted on Modrinth in the same way that they can currently be installed from CurseForge and FTB.

The implementation is highly based on the existing CurseForge/FTB installer code so it adds no new dependencies, which I see as an advantage.

Open Questions and Pre-Merge TODOs

[x] Add support for searching for and installing modpacks from Modrinth
[x] Add support for searching for and installing individual mods from Modrinth
[x] Add a proper way to show errors to the user (i.e. when a mod fails to download, or when the user tried to install an unsupported pack type like Quilt)
[x] Modrinth provides fallback download links for overrides. If an override file fails to download, the launcher should retry the download using given alternate links.
[ ] Waiting on #1400 so we can take immediate advantage of Modrinth's Quilt packs

Learning

I have read the Modrinth API docs (linked below).

Resources

Jul 04 '22 22:07 Pyroglyph

Modrinth said on Twitter that api user should have a User-Agent. Here the documentation: https://docs.modrinth.com/api-spec/#section/User-Agents

Jul 06 '22 23:07 AshtakaOOf

I found some issues with the build #1746 can you tell me if you fixed them or not? Here are the issues:

Mods manager doesn't automatically detect the modloader to download mods
Mods manager doesn't automatically detect which version of minecraft you are on I hope you can fix these issues, even if you said you were waiting for the other pull request to be done.

Jul 13 '22 18:07 AshtakaOOf

@AshtakaOOf While trying to check for those issues I found a few more, so it seems I still have more work to do on this.

Jul 13 '22 20:07 Pyroglyph

I would definetly recommend getting it working as soon as possible as more and more mods are moving to Modrinth

Jul 27 '22 22:07 Hedwig7s

Would recommend just adding a pull request after this to add QuiltMC support to the patch because there's been no activity on that pull request and alot of big mods are moving and it's starting to really get annoying

Jul 30 '22 20:07 Hedwig7s

Would recommend just adding a pull request after this to add QuiltMC support to the patch because there's been no activity on that pull request and alot of big mods are moving and it's starting to really get annoying

Me and Pyro had already talked about this before I started the PR :P

Aug 04 '22 15:08 Ecorous

I've come back after a few weeks off this project and suddenly it wasn't working. I did some investigation and found that when I merged this commit caused a total freeze (but not a crash) when opening the Manage window of an instance. It happens on both Windows and Linux on 2 different machines, so it's not isolated. I haven't figured out why yet.

I've rewritten the history of my branch to remove the times I merged from the master branch and that has stopped the issue, hence the recent force push.

Edit: The commit I mentioned earlier is the problem. Merging the latest master in breaks it, reverting that commit fixes it.

Sep 07 '22 18:09 Pyroglyph

Hello! I was wondering if you had any leads as to what the issue is? I wanted to take a crack at it and I'm curious if there was any work already put into resolving it.