reimplemented+simplified switchable server logging

don't know how well it interacts with `log` (or upcoming tracing), so this may be temporary and/or incomplete. But it works for my application code at the least (as opposed to library code)

server/main/src/configuration.rs

@@ -1,10 +0,0 @@
-use std::str::FromStr;
-
-use logging::{Level, error};
-
-pub fn handle_log_level_change<F: FnOnce(Level)>(log_level: String, callback: F) {
-    match Level::from_str(log_level.as_str()) {
-        Ok(level) => callback(level),
-        Err(_) => error!("got unexpected log level from config"; "level" => log_level),
-    };
-}

server/main/src/main.rs

@@ -3,12 +3,12 @@ use logging::{logger, FutureExt};
 use server::Server;
 use tower_lsp::LspService;
 
-mod configuration;
 mod navigation;
 
 #[tokio::main]
 async fn main() {
-    let _guard = logging::set_level(logging::Level::Debug);
+    // start with debug log level, and then adjust once we get the configuration from the client.
+    logging::set_level(logging::Level::Debug);
 
     let stdin = tokio::io::stdin();
     let stdout = tokio::io::stdout();