That's an FFI mechanism for Rustls the popular Rust TLS implementation (commonly used in Rust where say C or C++ programmers might use OpenSSL) So that's the component you would need if you've decided you want a Rust TLS implementation but, you actually want to use it from say, C++ instead.

I assume the parent is actually a Rust programmer, or at least, intend to use this from Rust, so, yeah, plain Rustls is an obvious choice. https://crates.io/crates/rustls

As Thomas Ptacek emphasised above, despite Botan saying it's "Crypto and TLS" if you think you might need some sort of "Crypto" rather than you just want to speak TLS, such libraries have way too many knobs and switches you don't understand, as does OpenSSL. The whole point of libsodium and similar libraries is to not have switches you don't need. Spell out a use case and deliver exactly what's needed for that use case, nothing else, no switches, no "optional" features.

Rust has a libsodium wrapper, which is especially useful if you either trust libsodium particularly or you have experience with those APIs, and also some similar but Rust flavor approaches where they don't give you all the knobs and switches just an API that makes sense for the specific use case you chose from their list - either the library is correct or it's not, no "What kind of idiot pushes the red button?" problems.