How to handle eager loading on REST API - php

Question

Imagine you have the following resources for example: Users, Posts and Comments (With typical relationship setup in laravel).
When fetching a single Post, you will have the following endpoint
GET /api/posts/1
// With route model binding
public function show(Post $post)
{
return $post;
}
This is fine if I only want the Post object, but in some pages in my application, I also need to load the User and the Comments associated with the Post.
How do you guys handle that kind of scenario?
1. Should I load everything in that endpoint like:
return $post->load(['user', 'comments.user']);
and call it a day? (nope)
2. Should I accept an additional parameter that will tell my controller to load the relationship based on that value?
// With route model binding
public function show(Request $request, Post $post)
{
// rel for "relationship"
if ($request->has('rel')) {
$post->load($request->input('rel'));
}
return $post;
}
with this approach I could do something like this:
GET /api/posts/1?rel=user
returns Post with User
or I could build an array of parameter with jquery's $.param(['user', 'comments.user'])
GET /api/posts/1?rel%5B%5D=user&rel%5B%5D=comments.user
returns Post with User + Comments.User
but anyone can easily mess with the 'rel' parameter so I also need to check that
¯\(°_o)/¯
3. Just create a new endpoint for every specific requirements. (what should your endpoint look like for the example above?).
I'm building a SPA with Angular + Laravel (just a self-consumed API) for my Internal Project when I encounter this pitfall. The second approach is what I currently using for basic fetching and I use the third approach for more complex requirements.
Any inputs are appreciated.