Update ServerRequest to accept server name (#3619)

* Update ServerRequest to accept server name

* Update docs to include Apache and nginx examples

* Test the server not containing a port

semconv/v1.16.0/httpconv/http.go

@@ -88,13 +88,28 @@ func ClientStatus(code int) (codes.Code, string) {
 }
 
 // ServerRequest returns attributes for an HTTP request received by a server.
+//
+// The server must be the primary server name if it is known. For example this
+// would be the ServerName directive
+// (https://httpd.apache.org/docs/2.4/mod/core.html#servername) for an Apache
+// server, and the server_name directive
+// (http://nginx.org/en/docs/http/ngx_http_core_module.html#server_name) for an
+// nginx server. More generically, the primary server name would be the host
+// header value that matches the default virtual host of an HTTP server. It
+// should include the host identifier and if a port is used to route to the
+// server that port identifier should be included as an appropriate port
+// suffix.
+//
+// If the primary server name is not known, server should be an empty string.
+// The req Host will be used to determine the server instead.
+//
 // The following attributes are always returned: "http.method", "http.scheme",
 // "http.flavor", "http.target", "net.host.name". The following attributes are
 // returned if they related values are defined in req: "net.host.port",
 // "net.sock.peer.addr", "net.sock.peer.port", "http.user_agent", "enduser.id",
 // "http.client_ip".
-func ServerRequest(req *http.Request) []attribute.KeyValue {
-	return hc.ServerRequest(req)
+func ServerRequest(server string, req *http.Request) []attribute.KeyValue {
+	return hc.ServerRequest(server, req)
 }
 
 // ServerStatus returns a span status code and message for an HTTP status code