Replica promotion in compute_ctl (#12183)

Add `/promote` method for `compute_ctl` promoting secondary replica to
primary,
depends on secondary being prewarmed.
Add `compute-ctl` mode to `test_replica_promotes`, testing happy path
only (no corner cases yet)
Add openapi spec for `/promote` and `/lfc` handlers

https://github.com/neondatabase/cloud/issues/19011
Resolves: https://github.com/neondatabase/cloud/issues/29807

test_runner/fixtures/endpoint/http.py

@@ -2,11 +2,12 @@ from __future__ import annotations
 
 import urllib.parse
 from enum import StrEnum
-from typing import TYPE_CHECKING, final
+from typing import TYPE_CHECKING, Any, final
 
 import requests
 from requests.adapters import HTTPAdapter
 from requests.auth import AuthBase
+from requests.exceptions import ReadTimeout
 from typing_extensions import override
 
 from fixtures.log_helper import log
@@ -102,6 +103,18 @@ class EndpointHttpClient(requests.Session):
 
         wait_until(offloaded)
 
+    def promote(self, safekeepers_lsn: dict[str, Any], disconnect: bool = False):
+        url = f"http://localhost:{self.external_port}/promote"
+        if disconnect:
+            try:  # send first request to start promote and disconnect
+                self.post(url, data=safekeepers_lsn, timeout=0.001)
+            except ReadTimeout:
+                pass  # wait on second request which returns on promotion finish
+        res = self.post(url, data=safekeepers_lsn)
+        res.raise_for_status()
+        json: dict[str, str] = res.json()
+        return json
+
     def database_schema(self, database: str):
         res = self.get(
             f"http://localhost:{self.external_port}/database_schema?database={urllib.parse.quote(database, safe='')}",