feat: add IsNullable and IsUndefined decorators

[d-lukutin]

Description

Sometimes it is necessary to clearly distinguish between null and undefined values. When using only IsOptional, parameters with null values may end up in the database.

Checklist

• [ x] the pull request title describes what this PR does (not a vague title like Update index.md)
• [ x] the pull request targets the default branch of the repository (develop)
• [ x] the code follows the established code style of the repository
  • npm run prettier:check passes
  • npm run lint:check passes
• [ x] tests are added for the changes I made (if any source code was modified)
• [ x] documentation added or updated
• [ x] I have run the project locally and verified that there are no errors