How to choose an owned vs. borrowed struct member

[scottmcm]

First, remember that "references in structs [are] the evil-hardmode of Rust that will ruin your day.".

But if you'd like some more nuanced guidelines, you might find this thread interesting:

Guidelines for heap data

It's different for the different guidelines. For #3 it's essentially 100% because of the "create and return" part. There's basically no reasonable way to have a fn foo<'a>() -> &'a str function -- either it leaks memory (obviously bad) or it can only return a string literal (so limited as to be largely irrelevant). (The exception here is if "create" doesn't apply. If it's actually returning subparts of a parameter -- substrings are the usual example -- in such a way that lifetime elision app…

As a specific place you might move slightly less to owned stuff, it's plausible that the methods are commonly string literals. So you could consider something like

pub struct Endpoint {
    pub uri: String,
    pub methods: Vec<Cow<'static, str>>, // e.g. "GET", "POST"
}

As that way you wouldn't need to allocate for common things.