Allow passing workspace configuration to the Language Server (#13)

This PR adds the ability to configure kotlin-language-server.

---------

Co-authored-by: Marshall Bowers <[email protected]>

Author: 424ever

README.md

@@ -1,3 +1,30 @@
 # zed-kotlin
 
 Kotlin language support for [Zed](https://github.com/zed-industries/zed).
+
+## Configuration
+
+Workspace configuration options can be passed to the language server via lsp
+settings in `settings.json`.
+
+The following example changes the JVM target from `default` (which is 1.8) to
+`17`:
+
+```json
+{
+  "lsp": {
+    "kotlin-language-server": {
+      "settings": {
+        "compiler": {
+          "jvm": {
+            "target": "17"
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+The full list of workspace configuration options can be found
+[here](https://github.com/fwcd/kotlin-language-server/blob/main/server/src/main/kotlin/org/javacs/kt/Configuration.kt).

src/kotlin.rs

@@ -1,6 +1,7 @@
 use std::fs;
+use zed::serde_json;
 use zed::LanguageServerId;
-use zed_extension_api::{self as zed, Result};
+use zed_extension_api::{self as zed, settings::LspSettings, Result};
 
 struct KotlinExtension {
     cached_binary_path: Option<String>,
@@ -83,6 +84,21 @@ impl zed::Extension for KotlinExtension {
             env: Default::default(),
         })
     }
+
+    fn language_server_workspace_configuration(
+        &mut self,
+        _language_server_id: &LanguageServerId,
+        worktree: &zed_extension_api::Worktree,
+    ) -> Result<Option<serde_json::Value>> {
+        let settings = LspSettings::for_worktree("kotlin-language-server", worktree)
+            .ok()
+            .and_then(|lsp_settings| lsp_settings.settings.clone())
+            .unwrap_or_default();
+
+        Ok(Some(serde_json::json!({
+            "kotlin": settings
+        })))
+    }
 }
 
 zed::register_extension!(KotlinExtension);