docs: restructure into topical sections and add the four most-asked-for pages (#3044)

docs_src/legacy_clients/tutorial003.py

@@ -0,0 +1,21 @@
+from mcp.server import MCPServer
+from mcp.server.mcpserver import Context
+
+mcp = MCPServer("Bookshop")
+
+STOCK = {"Dune": 3}
+
+
+@mcp.resource("stock://{title}")
+def stock(title: str) -> str:
+    """How many copies of one book are on the shelf."""
+    return f"{STOCK[title]} in stock"
+
+
+@mcp.tool()
+async def restock(title: str, copies: int, ctx: Context) -> str:
+    """Put copies of a book back on the shelf."""
+    STOCK[title] = STOCK.get(title, 0) + copies
+    await ctx.notify_resource_updated(f"stock://{title}")
+    await ctx.session.send_resource_updated(f"stock://{title}")
+    return f"{STOCK[title]} in stock"