[FLINK-37650] Enable Stale PR Github action

Signed-off-by: Thomas Cooper <[email protected]>

Author: tomncooper

.github/workflows/stale.yml

@@ -0,0 +1,61 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+
+# This workflow labels and then closes stale PRs that haven't seen attention
+# for several months.
+
+name: Stale PRs
+on:
+  schedule:
+    - cron: '15 6 * * *' # Run once a day at 6:15 UTC
+  workflow_dispatch:
+    inputs:
+      operationsPerRun:
+        description: 'Max GitHub API operations'
+        required: true
+        default: 20
+        type: number
+
+permissions:
+  issues: write
+  pull-requests: write
+  actions: write
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          operations-per-run: ${{ inputs.operationsPerRun || 500 }}
+          ascending: true
+          days-before-stale: 90
+          days-before-close: 30
+          stale-pr-label: 'stale'
+          stale-pr-message: |
+            This PR is being marked as stale since it has not had any activity in the last 90 days. 
+            If you would like to keep this PR alive, please leave a comment asking for a review. 
+            If the PR has merge conflicts, update it with the latest from the base branch.
+
+            If you are having difficulty finding a reviewer, please reach out to the 
+            community, contact details can be found here: https://flink.apache.org/what-is-flink/community/
+
+            If this PR is no longer valid or desired, please feel free to close it. 
+            If no activity occurs in the next 30 days, it will be automatically closed.
+          close-pr-label: 'closed-stale'
+          close-pr-message: |
+            This PR has been closed since it has not had any activity in 120 days. 
+            If you feel like this was a mistake, or you would like to continue working on it, 
+            please feel free to re-open the PR and ask for a review.

.gitignore

@@ -36,6 +36,7 @@ tools/flink
 tools/flink-*
 tools/releasing/release
 tools/japicmp-output
+.vscode/
 
 # Generated file, do not store in git
 flink-connector-kafka/.idea