Challenge 1: Params or Body? — Possible Solution
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(a) Filtering a product list by category — QUERY PARAMETER.
?category=electronics describes WHICH data to fetch on a GET request
— exactly the "filtering, sorting, pagination" use case this chapter
named for query parameters. There's no new data being created or sent
to the server to store.

(b) The full contents of a new blog post being created — REQUEST BODY.
This is actual data the server needs to store — a title, body text,
possibly much longer than would be reasonable or safe to cram into a
URL's query string. This belongs on a POST request's body, formatted
as JSON.

(c) A page number for pagination — QUERY PARAMETER. Like category
filtering, a page number describes which slice of an existing GET
result set to return (?page=2) — it's selecting data, not submitting
new data to be stored.