Proper Server Response Header Support

[rylev]

There are many HTTP response headers that we should be sending back to the client. Here is a list of headers that we may want to support for every single HTTP request. Note, this list may be incomplete and new ones should be added when discovered or removed when deemed not necessary.

• Content-Type
• Date
• Connection

[yoshuawuyts]

This is an interesting one to consider, because creating a new Response on the client is different from creating a new Response on the server. I wonder if this perhaps belongs in the documentation for the Response type, and then HTTP impls could then do this?

[yoshuawuyts]

Also I'm unsure about recommending people set the Server header; it seems like it could help make attacks easier: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Server