Integrate FastMCP

This commit integrates FastMCP, a high-level MCP server implementation originally written by Jeremiah Lowin,
into the official MCP SDK. It also updates dependencies and adds new dev dependencies.
It moves the existing SDK into a .lowlevel .

tests/server/fastmcp/prompts/test_manager.py

@@ -0,0 +1,107 @@
+import pytest
+from mcp.server.fastmcp.prompts.base import UserMessage, TextContent, Prompt
+from mcp.server.fastmcp.prompts.manager import PromptManager
+
+
+class TestPromptManager:
+    def test_add_prompt(self):
+        """Test adding a prompt to the manager."""
+
+        def fn() -> str:
+            return "Hello, world!"
+
+        manager = PromptManager()
+        prompt = Prompt.from_function(fn)
+        added = manager.add_prompt(prompt)
+        assert added == prompt
+        assert manager.get_prompt("fn") == prompt
+
+    def test_add_duplicate_prompt(self, caplog):
+        """Test adding the same prompt twice."""
+
+        def fn() -> str:
+            return "Hello, world!"
+
+        manager = PromptManager()
+        prompt = Prompt.from_function(fn)
+        first = manager.add_prompt(prompt)
+        second = manager.add_prompt(prompt)
+        assert first == second
+        assert "Prompt already exists" in caplog.text
+
+    def test_disable_warn_on_duplicate_prompts(self, caplog):
+        """Test disabling warning on duplicate prompts."""
+
+        def fn() -> str:
+            return "Hello, world!"
+
+        manager = PromptManager(warn_on_duplicate_prompts=False)
+        prompt = Prompt.from_function(fn)
+        first = manager.add_prompt(prompt)
+        second = manager.add_prompt(prompt)
+        assert first == second
+        assert "Prompt already exists" not in caplog.text
+
+    def test_list_prompts(self):
+        """Test listing all prompts."""
+
+        def fn1() -> str:
+            return "Hello, world!"
+
+        def fn2() -> str:
+            return "Goodbye, world!"
+
+        manager = PromptManager()
+        prompt1 = Prompt.from_function(fn1)
+        prompt2 = Prompt.from_function(fn2)
+        manager.add_prompt(prompt1)
+        manager.add_prompt(prompt2)
+        prompts = manager.list_prompts()
+        assert len(prompts) == 2
+        assert prompts == [prompt1, prompt2]
+
+    async def test_render_prompt(self):
+        """Test rendering a prompt."""
+
+        def fn() -> str:
+            return "Hello, world!"
+
+        manager = PromptManager()
+        prompt = Prompt.from_function(fn)
+        manager.add_prompt(prompt)
+        messages = await manager.render_prompt("fn")
+        assert messages == [
+            UserMessage(content=TextContent(type="text", text="Hello, world!"))
+        ]
+
+    async def test_render_prompt_with_args(self):
+        """Test rendering a prompt with arguments."""
+
+        def fn(name: str) -> str:
+            return f"Hello, {name}!"
+
+        manager = PromptManager()
+        prompt = Prompt.from_function(fn)
+        manager.add_prompt(prompt)
+        messages = await manager.render_prompt("fn", arguments={"name": "World"})
+        assert messages == [
+            UserMessage(content=TextContent(type="text", text="Hello, World!"))
+        ]
+
+    async def test_render_unknown_prompt(self):
+        """Test rendering a non-existent prompt."""
+        manager = PromptManager()
+        with pytest.raises(ValueError, match="Unknown prompt: unknown"):
+            await manager.render_prompt("unknown")
+
+    async def test_render_prompt_with_missing_args(self):
+        """Test rendering a prompt with missing required arguments."""
+
+        def fn(name: str) -> str:
+            return f"Hello, {name}!"
+
+        manager = PromptManager()
+        prompt = Prompt.from_function(fn)
+        manager.add_prompt(prompt)
+        with pytest.raises(ValueError, match="Missing required arguments"):
+            await manager.render_prompt("fn")