Function static_headers 

pub fn static_headers<I, N, V>(
    headers: I,
    slot: &CredentialSlot,
) -> Result<Headers>
where
    I: IntoIterator<Item = (N, V)>,
    N: Into<String>,
    V: Into<String>,

The headers a provider sends with every request: User-Agent: DEFAULT_USER_AGENT, then headers (a builder’s header(name, value) settings, in order), each replacing the headers of the same name before it, so header("user-agent", ..) replaces the default. Set them on each request with HttpRequest::with_headers.

These headers belong to one provider: a gateway’s routing header, a tenant tag, a beta flag. Credentials do not: they are refused here, as HttpRequest::apply_options refuses them in a request’s options, so a key always goes through the builder’s key setting or a per-request Credential, where it is scoped and redacted.

use allama_http::{CredentialPlacement, CredentialSlot, DEFAULT_USER_AGENT, config};

let slot = CredentialSlot::new("acme", CredentialPlacement::Bearer);
let headers = config::static_headers([("x-route", "eu")], &slot)?;
assert_eq!(headers.get("user-agent"), Some(DEFAULT_USER_AGENT));
assert_eq!(headers.get("x-route"), Some("eu"));

let err = config::static_headers([("x-api-key", "sk-acme")], &slot).unwrap_err();
assert!(matches!(err, allama::Error::Configuration { .. }));
assert!(!err.to_string().contains("sk-acme"));

Errors

An authored allama::Error::Configuration naming the header, never its value, when the name is not a valid header name, the value holds a character a header cannot carry (anything but visible ASCII, spaces and tabs), or the header carries a credential: it is on the exact credential list (is_credential_header), or slot writes or replaces it.