http2 alpn (#6815)

## Problem

Proxy already supported HTTP2, but I expect no one is using it because
we don't advertise it in the TLS handshake.

## Summary of changes

#6335 without the websocket changes.

test_runner/fixtures/neon_fixtures.py

@@ -27,6 +27,7 @@ from urllib.parse import quote, urlparse
 
 import asyncpg
 import backoff
+import httpx
 import jwt
 import psycopg2
 import pytest
@@ -2856,9 +2857,34 @@ class NeonProxy(PgProtocol):
         )
 
         if expected_code is not None:
-            assert response.status_code == kwargs["expected_code"], f"response: {response.json()}"
+            assert response.status_code == expected_code, f"response: {response.json()}"
         return response.json()
 
+    async def http2_query(self, query, args, **kwargs):
+        # TODO maybe use default values if not provided
+        user = kwargs["user"]
+        password = kwargs["password"]
+        expected_code = kwargs.get("expected_code")
+
+        connstr = f"postgresql://{user}:{password}@{self.domain}:{self.proxy_port}/postgres"
+        async with httpx.AsyncClient(
+            http2=True, verify=str(self.test_output_dir / "proxy.crt")
+        ) as client:
+            response = await client.post(
+                f"https://{self.domain}:{self.external_http_port}/sql",
+                json={"query": query, "params": args},
+                headers={
+                    "Content-Type": "application/sql",
+                    "Neon-Connection-String": connstr,
+                    "Neon-Pool-Opt-In": "true",
+                },
+            )
+            assert response.http_version == "HTTP/2"
+
+            if expected_code is not None:
+                assert response.status_code == expected_code, f"response: {response.json()}"
+            return response.json()
+
     def get_metrics(self) -> str:
         request_result = requests.get(f"http://{self.host}:{self.http_port}/metrics")
         request_result.raise_for_status()

test_runner/regress/test_proxy.py

@@ -554,3 +554,13 @@ def test_sql_over_http_pool_custom_types(static_proxy: NeonProxy):
         "select array['foo'::foo, 'bar'::foo, 'baz'::foo] as data",
     )
     assert response["rows"][0]["data"] == ["foo", "bar", "baz"]
+
+
+@pytest.mark.asyncio
+async def test_sql_over_http2(static_proxy: NeonProxy):
+    static_proxy.safe_psql("create role http with login password 'http' superuser")
+
+    resp = await static_proxy.http2_query(
+        "select 42 as answer", [], user="http", password="http", expected_code=200
+    )
+    assert resp["rows"] == [{"answer": 42}]