MCP Server - instrument `user_agent` header from MCP clients

[betegon]

Some hosts (that include clients) are starting to use the user_agent HTTP header as a way to identify themselves.

Example of a Cursor user agent - "User-Agent": "Cursor/1.1.6 (darwin arm64)"

[betegon]

MCP protocol let's client and server send their information in the initialization like this:

"clientInfo": {
  "name": "ExampleClient",
  "title": "Example Client Display Name",
  "version": "1.0.0"
}

and the same for the server

"serverInfo": {
  "name": "ExampleServer",
  "title": "Example Server Display Name",
  "version": "1.0.0"
},

So we'll be getting the information from there instead of the http header user_agent