Use slf4j logger instead of JUL

This fixes logging issues in certain environments.
Also replace stacktrace printing with logging it.

src/main/java/net/azisaba/kuvel/Kuvel.java

@@ -14,7 +14,6 @@
 import java.nio.file.Path;
 import java.util.Objects;
 import java.util.concurrent.TimeUnit;
-import java.util.logging.Logger;
 import lombok.Getter;
 import net.azisaba.kuvel.config.KuvelConfig;
 import net.azisaba.kuvel.discovery.impl.redis.RedisLoadBalancerDiscovery;
@@ -24,6 +23,7 @@
 import net.azisaba.kuvel.redis.ProxyIdProvider;
 import net.azisaba.kuvel.redis.RedisConnectionLeader;
 import net.azisaba.kuvel.redis.RedisSubscriberExecutor;
+import org.slf4j.Logger;
 
 @Plugin(
     id = "kuvel",
@@ -63,8 +63,7 @@ public void onProxyInitialization(ProxyInitializeEvent event) {
     try {
       kuvelConfig.load();
     } catch (Exception e) {
-      logger.severe("Failed to load config file. Plugin feature will be disabled.");
-      e.printStackTrace();
+      logger.error("Failed to load config file. Plugin feature will be disabled.", e);
       return;
     }
 

src/main/java/net/azisaba/kuvel/config/KuvelConfig.java

@@ -38,7 +38,8 @@ public void load() throws IOException {
       } catch (NumberFormatException e) {
         plugin
             .getLogger()
-            .warning("Invalid port number for Redis connection specified in KUVEL_REDIS_CONNECTION_PORT environment variable. Using port " + port + " from config.yml.");
+            .warn(
+                "Invalid port number for Redis connection specified in KUVEL_REDIS_CONNECTION_PORT environment variable. Using port " + port + " from config.yml.");
       }
     }
     String username = env.getOrDefault("KUVEL_REDIS_CONNECTION_USERNAME", conf.getString("redis.connection.username"));
@@ -48,7 +49,7 @@ public void load() throws IOException {
       redisEnabled = false;
       plugin
           .getLogger()
-          .warning(
+          .warn(
               "Redis is enabled, but hostname or port is invalid. Redis sync will be disabled.");
     } else {
       redisConnectionData = new RedisConnectionData(hostname, port, username, password);