Add workflow for automatic update (#145)

Author: sonallux

.github/workflows/update.yml

@@ -0,0 +1,73 @@
+name: Update Wrapper
+on:
+  schedule:
+    # runs every day at 02:23 UTC
+    - cron: '23 2 * * *'
+  workflow_dispatch:
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Setup java
+        uses: actions/setup-java@v2
+        with:
+          java-version: 17
+          distribution: 'zulu'
+          cache: 'maven'
+      - name: Get latest fixed open api definition
+        id: latest-openapi
+        uses: actions/github-script@v6
+        with:
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          result-encoding: string
+          script: |
+            const response = await github.rest.repos.getLatestRelease({
+              owner: 'sonallux',
+              repo: 'spotify-web-api',
+            });
+            const assetName = 'fixed-spotify-open-api.yml';
+            const asset = response.data.assets.find(asset => asset.name === assetName);
+            const browserDownloadUrl = asset?.browser_download_url;
+            if (!browserDownloadUrl) {
+              core.setFailed('Latest release did not contain the correct asset!');
+            }
+            return browserDownloadUrl;
+      - name: Download Spotify's OpenAPI
+        run: wget -O spotify-web-api-java-generator/fixed-spotify-open-api.yml ${{ steps.latest-openapi.outputs.result }}
+      - name: Build generator
+        run: ./mvnw -B -DskipTests package -Pcli
+      - name: Generate Java wrapper
+        run: ./generate-java-wrapper.sh
+      - name: Create Pull Request
+        id: cpr
+        uses: peter-evans/create-pull-request@v3
+        with:
+          # Use a PAT so GitHub actions are triggered on the PR
+          token: ${{ secrets.GH_REPO_TOKEN }}
+          commit-message: 'Update to fixed-spotify-open-api.yml'
+          branch: 'openapi-update'
+          delete-branch: true
+          base: main
+          author: 'sonallux <13821543+sonallux@users.noreply.github.com>'
+          title: 'Update to fixed-spotify-open-api.yml'
+          body: |
+            Automated update of `fixed-spotify-open-api.yml`
+
+            Generated by [this workflow run](https://github.com/sonallux/spotify-web-api-java/actions/runs/${{ github.run_id }}).
+      - name: Check outputs
+        run: 'echo "Pull Request ${{ steps.cpr.outputs.pull-request-operation }}: ${{ steps.cpr.outputs.pull-request-url }}"'
+      - name: Comment on PR
+        if: steps.cpr.outputs.pull-request-operation == 'created'
+        uses: actions/github-script@v6
+        with:
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          script: |
+            github.rest.issues.createComment({
+              issue_number: ${{ steps.cpr.outputs.pull-request-number }},
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: "@sonallux fixed-spotify-open-api.yml has been updated!"
+            })