Function notmuch_sys::notmuch_database_get_config

pub unsafe extern "C" fn notmuch_database_get_config(
    db: *mut notmuch_database_t, 
    key: *const c_char, 
    value: *mut *mut c_char
) -> notmuch_status_t

retrieve config item 'key', assign to 'value'

keys which have not been previously set with n_d_set_config will return an empty string.

return value is allocated by malloc and should be freed by the caller.

@since libnotmuch 4.4 (notmuch 0.23)