Clarify events backend project scope and cart design expectations

[oleksiybondar]

Updates the events-startup-project docs to remove ambiguity around MVP scope, API expectations, and database design.
Key clarifications include:

• required vs optional Week 5 backend features
• reserved-word naming guidance for schema design
• backend-persisted carts for both guest and authenticated users
• one-active-cart expectations and nullable cart.user_id hint
• default cart-line route/key design, with composite-key design noted as an alternative
• search via query parameters on GET /api/events
• explicit note that inventory is intentionally unlimited for this project

[adamblanchard]

thanks for the quick changes and clarifications! Overall i like the idea of this section, also for future use to add tips as we discover new things that we can guide trainees further on.

My main suggestion is to remove the scope/mvp section and update other docs first.

[adamblanchard]

This scope section looks like it's repeating some things already written elsewhere (e.g. admin optional scope is already written above).

Is there anything in here that's not already described above or in the main project readme?

If so, i suggest we update the main readme (for deliverables) and the requirements above (for scope) rather than create another list that trainees need to check (mostly) the same things.

[oleksiybondar]

I was trying to solves some of Alis unclarities, but yeah its written elsewhere, so we can remove it

[adamblanchard]

I like the idea of this "tips" section for some extra help :)