Replace httpx and httpx-sse with httpx2 (#2972)

Co-authored-by: Max Isbey <224885523+maxisbey@users.noreply.github.com>

src/mcp/server/extension.py

@@ -7,7 +7,7 @@ contribution kinds: tools, resources, new request methods, and one `tools/call`
 interceptor. The server never hands itself to an extension; the extension
 declares what it adds, and the server consumes it.
 
-The shape follows the HTTPX `Transport`/`Auth` pattern: a narrow base class whose
+The shape follows the httpx2 `Transport`/`Auth` pattern: a narrow base class whose
 methods have sensible defaults, so an extension overrides only what it needs. A
 purely additive extension (Apps) overrides `tools`/`resources`; an interceptive
 one overrides `methods`/`intercept_tool_call`.

src/mcp/server/mcpserver/resources/types.py

@@ -9,7 +9,7 @@ from typing import Any
 
 import anyio
 import anyio.to_thread
-import httpx
+import httpx2
 import pydantic
 import pydantic_core
 from mcp_types import Annotations, Icon, InputRequiredResult
@@ -170,7 +170,7 @@ class HttpResource(Resource):
 
     async def read(self) -> str | bytes:
         """Read the HTTP content."""
-        async with httpx.AsyncClient() as client:  # pragma: no cover
+        async with httpx2.AsyncClient() as client:  # pragma: no cover
             response = await client.get(self.url)
             response.raise_for_status()
             return response.text