feat: Make it easy for a self-hosted version to set the plan features

[istarkov]

Description

closes #3400

+ on dev login its now possible to add any email
like
{code}:[email protected] to login as other user

Steps for reproduction

Login on main with {code}:[email protected]

• See no plan

---

Login on main as usual

• See user has plan

---

Login locally
See user has plan

Code Review

• hi @kof, I need you to do
  • conceptual review (architecture, feature-correctness)
  • detailed review (read every line)
  • test it on preview

Before requesting a review

• made a self-review
• added inline comments where things may be not obvious (the "why", not "what")

Before merging

• tested locally and on preview environment (preview dev login: 5de6)
• updated test cases document
• added tests
• if any new env variables are added, added them to .env.example and the builder/env-check.js if mandatory