JetBrains Plugin (official or community)

This thread is to help those looking to use Expert LSP with JetBrains IDEs, such as IntelliJ IDEA/RubyMine/PyCharm/WebStorm/etc.

Users also might have been using the IntelliJ Elixir plugin previously, but given the size of the plugin, maintainership burden, IntelliJ API deprecations/updates/changes in 2024.x/2025.x causing the plugin to effectively not work without massive effort, this is a great time to now figure out how best to integrate.

The current plan is:

1. Investigate using the [LSP4IJ Plugin](https://github.com/redhat-developer/lsp4ij) as a base.
2. If there needs to be a companion/helper plugin created, let's make one, as the `intellij-elixir` plugin is quite old and not based on "modern practices" JetBrains is now promoting (which is great, their recent push for a better ecosystem is great).

> The official LSP plugin from JetBrains was only available in their paid/ultimate IDEs.. until 2 days ago! https://blog.jetbrains.com/platform/2025/09/the-lsp-api-is-now-available-to-all-intellij-idea-users-and-plugin-developers/