[ci] Use shared maintainer check for discord notifications (#32101)

Uses the shared maintainer check workflow across the various workflows
that need it
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/32101).
* __->__ #32101
* #32100

.github/workflows/compiler_discord_notify.yml

@@ -2,14 +2,17 @@ name: (Compiler) Discord Notify
 
 on:
   pull_request_target:
-    types: [labeled]
     paths:
       - compiler/**
       - .github/workflows/compiler_**.yml
 
 jobs:
+  check_maintainer:
+    uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
+
   notify:
-    if: ${{ github.event.label.name == 'React Core Team' }}
+    if: ${{ needs.check_maintainer.outputs.is_core_team }}
+    needs: check_maintainer
     runs-on: ubuntu-latest
     steps:
       - name: Discord Webhook Action

.github/workflows/runtime_discord_notify.yml

@@ -2,14 +2,17 @@ name: (Runtime) Discord Notify
 
 on:
   pull_request_target:
-    types: [labeled]
     paths-ignore:
       - compiler/**
       - .github/workflows/compiler_**.yml
 
 jobs:
+  check_maintainer:
+    uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
+
   notify:
-    if: ${{ github.event.label.name == 'React Core Team' }}
+    if: ${{ needs.check_maintainer.outputs.is_core_team }}
+    needs: check_maintainer
     runs-on: ubuntu-latest
     steps:
       - name: Discord Webhook Action

.github/workflows/shared_check_maintainer.yml

@@ -0,0 +1,35 @@
+name: (Shared) Check maintainer
+
+on:
+  workflow_call:
+    outputs:
+      is_core_team:
+        value: ${{ jobs.check_maintainer.outputs.is_core_team }}
+
+env:
+  TZ: /usr/share/zoneinfo/America/Los_Angeles
+  # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
+  SEGMENT_DOWNLOAD_TIMEOUT_MINS: 1
+
+jobs:
+  check_maintainer:
+    runs-on: ubuntu-latest
+    outputs:
+      is_core_team: ${{ steps.check_if_actor_is_maintainer.outputs.result }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Check if actor is maintainer
+        id: check_if_actor_is_maintainer
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const fs = require('fs');
+            const actor = '${{ github.actor }}';
+            const data = await fs.readFileSync('./MAINTAINERS', { encoding: 'utf8' });
+            const maintainers = new Set(data.split('\n'));
+            if (maintainers.has(actor)) {
+              console.log(`🟢 ${actor} is a maintainer`);
+              return true;
+            }
+            console.log(`🔴 ${actor} is NOT a maintainer`);
+            return null;

.github/workflows/shared_label_core_team_prs.yml

@@ -0,0 +1,29 @@
+name: (Shared) Label Core Team PRs
+
+on:
+  pull_request_target:
+
+env:
+  TZ: /usr/share/zoneinfo/America/Los_Angeles
+  # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
+  SEGMENT_DOWNLOAD_TIMEOUT_MINS: 1
+
+jobs:
+  check_maintainer:
+    uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
+
+  label:
+    if: ${{ needs.check_maintainer.outputs.is_core_team }}
+    runs-on: ubuntu-latest
+    needs: check_maintainer
+    steps:
+      - name: Label PR as React Core Team
+        uses: actions/github-script@v7
+        with:
+          script: |
+            github.rest.issues.addLabels({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: ${{ github.event.number }},
+              labels: ['React Core Team']
+            });