pub fn case_alias_key(key: &str) -> Option<String>Expand description
Return a lowercase case-alias for key when case-insensitive aliasing applies.
The aliasing rule: keys containing _ (channel variables such as
variable_*, and SIP passthrough headers such as sip_h_* / sip_i_*)
are excluded from case-insensitive aliasing because their suffix encodes
original SIP wire casing that must be preserved verbatim. All other keys
(dash-separated event and framing headers) may be looked up case-insensitively
via their lowercase form.
Returns Some(key.to_ascii_lowercase()) when aliasing applies, None for
underscore-containing keys.