Add OpenAPI CI

Signed-off-by: jld3103 <jld3103yt@gmail.com>

.github/workflows/openapi.yml

@@ -0,0 +1,38 @@
+name: OpenAPI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - stable*
+
+jobs:
+  openapi:
+    runs-on: ubuntu-latest
+
+    if: ${{ github.repository_owner != 'nextcloud-gmbh' }}
+
+    steps:
+      -   name: Checkout
+          uses: actions/checkout@v3
+
+      -   name: Set up php
+          uses: shivammathur/setup-php@v2
+          with:
+            php-version: '8.2'
+            extensions: xml
+            coverage: none
+          env:
+            GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      -   name: Composer install
+          run: composer i
+
+      -   name: OpenAPI checker
+          run: |
+            composer exec generate-spec
+            if [ -n "$(git status --porcelain openapi.json)" ]; then
+                git diff
+                exit 1
+            fi