#PLAT-3105 Add retrieving child info from user structure
Created by: ITDarkUFO
- Added UserHierarchy (mlm_User) entity to core
 - Registered UsersHierarchy as DbSet in AppDbContext
 - Introduced method to determine user level in mentor hierarchy
 - Created ChildUserDto to encapsulate child user details with mentorship level
 - Updated documentation for new methods, and enhanced for GetUserById
 
Jira Issue
[!IMPORTANT] This branch (
feat/get-user-by-id) is based onrefactor/move-fetching-to-core-servicesand depends on its changes. Make surerefactor/move-fetching-to-core-servicesis merged before merging