This effect of <'a> spreading everywhere is very frequently a novice mistake of putting temporary scope-bound loans (AKA references) in structs that aren't temporary views themselves.

People used to C or C++ perspective tend to reflexively (over)use references to avoid copying, but references in Rust are to avoid owning, and not-copying is handled in different ways.

BTW, apart from edgiest of edge cases, &String is a useless type in Rust, because String already stores data "by reference" and is never implicitly copied. For loans it's generally better to deref to &str.