Implements outputSchema validation (#566)

* feat: implement output schema validation

* fix: calculator example comply MCP spec

* refactor: merge cached_schema_for_output into schema_for_output

examples/servers/src/calculator_stdio.rs

@@ -0,0 +1,26 @@
+use anyhow::Result;
+use common::calculator::Calculator;
+use rmcp::{ServiceExt, transport::stdio};
+use tracing_subscriber::{self, EnvFilter};
+mod common;
+
+/// npx @modelcontextprotocol/inspector cargo run -p mcp-server-examples --example servers_calculator_stdio
+#[tokio::main]
+async fn main() -> Result<()> {
+    // Initialize the tracing subscriber with file and stdout logging
+    tracing_subscriber::fmt()
+        .with_env_filter(EnvFilter::from_default_env().add_directive(tracing::Level::DEBUG.into()))
+        .with_writer(std::io::stderr)
+        .with_ansi(false)
+        .init();
+
+    tracing::info!("Starting Calculator MCP server");
+
+    // Create an instance of our calculator router
+    let service = Calculator::new().serve(stdio()).await.inspect_err(|e| {
+        tracing::error!("serving error: {:?}", e);
+    })?;
+
+    service.waiting().await?;
+    Ok(())
+}