[Keyserver/rust] Improve debugging

Summary:
This was useful in helping track down
https://linear.app/comm/issue/ENG-4418. Would like to see these changes
persisted so if errors do arise in the future, we get more than nothing

Test Plan:
```
cd keyserver
RUST_LOG=debug yarn dev
```

Reviewers: bartek, varun

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8587

keyserver/addons/rust-node-addon/src/identity_client/login.rs

@@ -27,7 +27,7 @@ pub async fn login_user(
   let mut client_login = Login::new();
   let opaque_login_request = client_login
     .start(&password)
-    .map_err(|_| Error::from_status(Status::GenericFailure))?;
+    .map_err(|_| Error::from_reason("Failed to create opaque login request"))?;
 
   let login_start_request = OpaqueLoginStartRequest {
     opaque_login_request,
@@ -51,26 +51,30 @@ pub async fn login_user(
     }),
   };
 
+  debug!("Starting login to identity service");
   let login_start_response = identity_client
     .login_password_user_start(login_start_request)
     .await
     .map_err(handle_grpc_error)?
     .into_inner();
 
+  debug!("Received login response from identity service");
   let opaque_login_upload = client_login
     .finish(&login_start_response.opaque_login_response)
-    .map_err(|_| Error::from_status(Status::GenericFailure))?;
+    .map_err(|_| Error::from_reason("Failed to finish opaque login request"))?;
   let login_finish_request = OpaqueLoginFinishRequest {
     session_id: login_start_response.session_id,
     opaque_login_upload,
   };
 
+  debug!("Attempting to finalize opaque login exchange with identity service");
   let login_finish_response = identity_client
     .login_password_user_finish(login_finish_request)
     .await
     .map_err(handle_grpc_error)?
     .into_inner();
 
+  debug!("Finished login with identity service");
   let user_info = UserLoginInfo {
     user_id: login_finish_response.user_id,
     access_token: login_finish_response.access_token,

keyserver/src/user/login.js

@@ -172,6 +172,7 @@ async function registerOrLogin(): Promise<IdentityInfo> {
     ]);
     return identity_info;
   } catch (e) {
+    console.warn('Failed to login user: ' + getMessageForException(e));
     try {
       const identity_info = await rustAPI.registerUser(
         userInfo.username,