append
Appends a new header with name @name and value @value to @hdrs.
(If there is an existing header with name @name, then this creates a second one, which is only allowed for list-valued headers; see also method@MessageHeaders.replace.)
The caller is expected to make sure that @name and @value are syntactically correct.
Parameters
name
the header name to add
value
the new value of @name