Java Spring-Boot & Core-Java senior 4 vtiger API implementation

We look for Java Spring-Boog and Core-Java senior expert developer

Your job will be to implement requirements which are mutually agreed on this API
https://help.vtiger.com/article/147111249-Rest-API-Manual

Mandatory!!!!
You have to have a installed vtiger on your local environment to be able to use it properly and to test it properly!
you can run locally via:
https://hub.docker.com/r/javanile/vtiger

Milestones
MS1:
Implement a rest api call to
- find all users and return the users as full DTO (use jsonschema2pojo to get all fields generated)
List<UserDTO> findAllUsers()
List<UserDTO> findUsers(List<UserDTO> pUsersByExampleToFind)
- add users
List<UserDTO> addUsers(List<UserDTO> pUsersToAdd)
- update update users
List<UserDTO> updateUsers(List<UserDTO> pUsersToUpdate)
- block/ban users
List<UserDTO> blockUsers(List<UserDTO> pUsersToDelete)
- delete users
List<UserDTO> deleteUsers(List<UserDTO> pUsersToDelete)


MS2:
- same as above but for groups
- operations to add or remove users from specific groups (as set operations)
- same for assigning users to roles

Implementations:
- a Interface representing the above methods
- the impl of the interface
- the DTOs are hardcoded examples in multiple JUnit tests, so that the JUnit tests is basically your "main" method replacement with multiple entry points

NO UI for now required!
NO database required!
No REST endpoint exposing for the above named methods required! (only consuming the apis in the given links)

Your background is:
- multiple years of experience with Java
- multiple years of experience with REST APIs

If you are a good fit, you are open to get more tasks about implementing solutions fully on your own (e.g. with your team)

Budget?
will not be disclosed, place your best bid to get considered

What is next?
We will share you a NDA and afterwards a paid test task.

Payment?
- you estimate in a WBS (optimistic, expected, pessimistic, where optimistic < expected < pessimistic) after getting the task
- we discuss about clearances and effort
- we mutually agree to effort
- we assign you the task after mutually agreed
- you implement & delivery
- we pay
(basically the rules of freelancer)

Closed book vs open book?
We work only on open book.
Closed book means you are unwilling to define a WBS for the work and you add only a price tag to the task.
We are sorry we will not hire you in such a case!

Deliveries?
- in our on premise git (access will be granted to you)
- full sources
- maven
- libs, need prior confirm and we prefer to use mostly latest stable versions
- JDK 17 (mostly LTS)
- your api access code working on our end