Added database connection, added test and start with Testcontainers.

src/main/java/util/DatabaseConnection.java

@@ -0,0 +1,33 @@
+package util;
+
+import com.zaxxer.hikari.HikariConfig;
+import com.zaxxer.hikari.HikariDataSource;
+import io.github.cdimascio.dotenv.Dotenv;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+
+public class DatabaseConnection {
+
+    private static Dotenv dotenv = Dotenv.load();
+
+    private static HikariConfig config = new HikariConfig();
+    private static HikariDataSource ds;
+
+    static {
+        config.setJdbcUrl(dotenv.get("JDBC"));
+        config.setUsername(dotenv.get("POSTGRES_USER"));
+        config.setPassword(dotenv.get("POSTGRES_PASSWORD"));
+        config.setDriverClassName("org.postgresql.Driver");
+        config.setMaximumPoolSize(10);
+        config.setMinimumIdle(2);
+        ds = new HikariDataSource(config);
+    }
+
+    private DatabaseConnection() {};
+
+    public static Connection getConnection() throws SQLException {
+        return ds.getConnection();
+    }
+
+}