Check robustness to missing fields: servers should reject and otherwise ignore
bad requests.

Fixed bugs:
- No id in 'initialize' should not panic (#197).
- No id in 'ping' should not panic (#194).

TODO:
- No params in 'initialize' should not panic (#195).

-- prompts --
code_review

-- client --
{
  "jsonrpc": "2.0",
  "method": "initialize",
  "params": {
    "protocolVersion": "2024-11-05",
    "capabilities": {},
    "clientInfo": { "name": "ExampleClient", "version": "1.0.0" }
  }
}
{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "initialize",
  "params": {
    "protocolVersion": "2024-11-05",
    "capabilities": {},
    "clientInfo": { "name": "ExampleClient", "version": "1.0.0" }
  }
}
{"jsonrpc":"2.0", "method":"ping"}

-- server --
{
	"jsonrpc": "2.0",
	"id": 2,
	"result": {
		"capabilities": {
			"completions": {},
			"logging": {},
			"prompts": {
				"listChanged": true
			}
		},
		"protocolVersion": "2024-11-05",
		"serverInfo": {
			"name": "testServer",
			"version": "v1.0.0"
		}
	}
}