FOSRestBundle | Bundle provides various tools to rapidly develop RESTful API | REST library

I have two entity classes: Product and Price. Product has many Prices. The relations are defined as (only relevant code is shown):

Product.php

I am new to Symfony (5.3) and would like to extend the RequestBodyParamConverter (FOSRestBundle 3.0.5) to create a REST api. Using @ParamConverter annotation with the RequestBodyParamConverter works fine. However, I would like to create a custom converter, which does the exact same job as RequestBodyParamConverter plus a little extra work.

My first guess was to simply extend RequestBodyParamConverter and provide my custom subclass in the @ParamConverter annotation. However, RequestBodyParamConverter is defined as final and thus cannot be extended...

Injecting RequestBodyParamConverter / fos_rest.request_body_converter into a custom converter class (see example below) also fails because the service cannot be found. I assume this is because it is defined a private?

So, my last idea was to create a RequestBodyParamConverter inside my custom converter class. While this works, I am not sure if this is the right way to solve this problem. This way RequestBodyParamConverter is created twice. This is nothing special of course, but is this the Symfony way to solve this or are there other solutions?

Example:

Inject RequestBodyParamConverter in custom converter class

I have a problem with fresh install of Swagger and FosRestBundle on Symfony 5 app. I have this error :

Last days I try to upgrade my project step by step. I have Symfony 2.8, composer 2. Lately I found rector/rector package for upgrading, but there was conflicts when I try to install it. Next I try to install rector/rector-prefixed. It also gives many problems with installation, but after research I've update my php version to 7.4 and it goes good. I've made composer update and install, but in the meantime new error shows up. With AppKernel. Before there was everything good and the app works fine. Now I've got message in the browser: Composer detected issues in your platform: "Your Composer dependencies require a PHP version ">= 7.4.0". "

And in the console after every command (for example: php app/console list) now I'm getting this message:

I have a nested JSON object that I am trying to send to a Symfony API which is using FOSRestBundle.

I have a problem with a Symfony 3.4 application where users can vote entries from other users. It uses FOSRestBundle for APIs and Doctrine for data persistance. The code is very simple:

I'm trying to creating an API REST with the bundle FOSRestBundle (SF5). I've an entity "Categorie" which can have an parent "Categorie". Here is the entity :

Im working on a FormType that will be populated through JSON (FOSRestBundle). This form has a CollectionType and I have the entry_type set to another FormType.

But whatever I try, I end up with the error: This form should not contain extra fields.

ProductCollection:

I was trying to install FOSRestBundle on Symfony 5 using composer but got the following error message:

friendsofsymfony/rest-bundle 2.7.1 requires symfony/config ^3.4|^4.3

Is it possible to manually install FOSRestBundle with Symfony 5; as it seems it will not be updated and instead API Platform will be maintained in future?

I don't want to use API Platform as it has lot of stuff not required by my project.