Macro http_variable_get

macro_rules! http_variable_get {
    ( $name: ident, $handler: expr ) => { ... };
}

Define a static variable evaluator.

The get handler is responsible for evaluating a variable in the context of a specific request. Variable evaluators accept a Request input argument and two output arguments: ngx_variable_value_t and usize. Variables: https://nginx.org/en/docs/dev/development_guide.html#http_variables