feat(UserManager): Update constructor for storage systems

This commit updates the `UserManager` class constructor. The previous constructor was refactored to remove the multiple if-else statements for type checking and replaced with a `switch` statement. Additionally, the new constructor adds fields for `File directory` , `Connection conn`, and `MongoDB db`, depending on the storage type. This allows for more flexibility and easier maintenance of the class. Finally, the `usersDirectory` field is now created if it does not exist. This change is a feature addition and improves the class's usability.

database/src/main/java/com/georgev22/library/utilities/UserManager.java

@@ -51,7 +51,7 @@ public class UserManager {
      *
      * @param type           the type of storage system to be used (JSON, SQL or MONGODB)
      * @param obj            the object to be used for storage (File for JSON, Connection for SQL and MongoDB for MONGODB)
-     * @param collectionName the name of the collection to be used for MONGODB, null for other types
+     * @param collectionName the name of the collection to be used for MONGODB and SQL, null for other types
      */
     public UserManager(@NotNull Type type, Object obj, @Nullable String collectionName) {
         this.type = type;
@@ -93,7 +93,7 @@ public UserManager registerObjectMapSerializer() {
     }
 
     /**
-     * Registers type adapters for the specified classes using the GsonBuilder.
+     * Register type adapters for the specified classes using the GsonBuilder.
      *
      * @param pairs a PairDocument containing the Class and type adapter pairs to register
      * @return this UserManager