Add a header entry for the given name.
If there was no entry for that header name before, the value will be used as-is. In case of an existing entry, a String array will be created, adding the given value (more specifically, its toString representation) as further element.
Multiple values can only be stored as list of Strings, following the Servlet spec (see {@code getHeaders} accessor). As alternative torepeated {@code addHeader} calls for individual elements, you canuse a single call with an entire array or Collection of values as parameter.
@see #getHeaderNames
@see #getHeader
@see #getHeaders
@see #getDateHeader
@see #getIntHeader