Update documentation for extra lazy associations

[diegobanos]

Clarified conditions for using Collection methods with extra lazy associations that won't initialize the Collection.

I was running some manual tests locally and it seems like EXTRA_LAZY collections get initialized when calling Collection::get() and Collection::containsKey() unless an indexBy field is specified. This wasn't clear in the docs.

[greg0ire]

unless

🤔 did you mean to write "only if"?

Can you show me the tests you ran and the outcome, so that I understand better what you mean?

[diegobanos]

unless

🤔 did you mean to write "only if"?

Can you show me the tests you ran and the outcome, so that I understand better what you mean?

I was reading this documentation page and comparing how LAZY and EXTRA_LAZY associations behave to understand it better. The tests were simply to call each method on a LAZY and an EXTRA_LAZY collection, and then inspecting if the collection became initialized or not. When testing the EXTRA_LAZY collection, I was surprised that calling Collection#containsKey($key) or Collection#get($key) would initialize the collection. I then found out that if I defined an indexBy to the EXTRA_LAZY collection, it was accurate that those two methods wouldn't initialize the entire collection.

The reason I submitted this MR is because I am assuming this is expected behavior but it was just not clear (to me) when reading the docs that this is how EXTRA_LAZY collections behave, and I wanted to help future readers. If this is unexpected behavior, I can create a small reproducible of this.

[diegobanos]

🤔 did you mean to write "only if"?

Yeah, I think I said the opposite of what I meant to say... Having an indexBy defined on the EXTRA_LAZY collection is a requirement for Collection#containsKey($key) or Collection#get($key) to not initialize the entire collection.

[greg0ire]

I think it's expected behavior.