feat: mock API server for testing server SDKs (#4627)

* feat: mock API server for testing server SDKs

* fixed lint

.github/workflows/test-server-docker.yaml

@@ -0,0 +1,53 @@
+# Copyright 2026 LiveKit, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Builds and publishes the SDK conformance test server (cmd/test-server) to
+# Docker Hub as livekit/test-server:latest on every push to master. The server
+# SDK repos boot this image in their CI to run region-failover tests.
+name: Release Test Server to Docker
+
+permissions:
+  contents: read
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - master
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4
+
+      - name: Login to DockerHub
+        uses: docker/login-action@650006c6eb7dba73a995cc03b0b2d7f5ca915bee # v4
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@f9f3042f7e2789586610d6e8b85c8f03e5195baf # v7
+        with:
+          context: .
+          file: cmd/test-server/Dockerfile
+          push: true
+          platforms: linux/amd64,linux/arm64
+          # Each build overrides the latest tag so SDK CI always boots the
+          # current mock server.
+          tags: livekit/test-server:latest