MDEV-38546: Automatically label new unlabeled pull requests

 with foundation/corporation/external contribution

The MariaDB server repository uses certain pull request labels as queue markers
 for incoming pull requests as follows:
 - External Contribution: for all external contributions
- MariaDB Corporation: for employees of the MariaDB corporation
- MariaDB Foundation: for the employees of the MariaDB foundation

Right now, when a new pull request is filed, these tags need to be applied
manually.
However a large % of these manual assignments can be automated by checking
if the author is in https://github.com/orgs/MariaDB/teams/staff
or in https://github.com/orgs/MariaDB/teams/developers.

If they are in staff "MariaDB Foundation" is assigned.

if they are not in staff, but are in developers, "MariaDB Foundation" is assigned.

If they are in neither staff not developers, "External Contribution" is assigned.

A github workflow is created to do the assignments. It is being triggered
every day at 2AM. Or it can be triggered manually.

Author: gkodinov

.github/workflows/label_recent_prs.yaml

@@ -0,0 +1,96 @@
+name: Label recent pull requests
+
+on:
+  schedule:
+    - cron: "0 2 * * *" # 02:00 UTC daily
+  workflow_dispatch:    # allow manual runs
+
+permissions:
+  contents: read
+  pull-requests: write
+  issues: write
+
+jobs:
+  label-prs:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Label recent pull requests
+        uses: actions/github-script@v7
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const foundationOrg = "MariaDB/teams/staff";
+            const developersOrg = "MariaDB/teams/developers";
+
+            const now = new Date();
+            const since = new Date(now.getTime() - 7 * 24 * 60 * 60 * 1000);
+
+            const owner = context.repo.owner;
+            const repo = context.repo.repo;
+
+            // Get open PRs
+            const prs = await github.paginate(
+              github.rest.pulls.list,
+              {
+                owner,
+                repo,
+                state: "open",
+                per_page: 100
+              }
+            );
+
+            for (const pr of prs) {
+              const createdAt = new Date(pr.created_at);
+
+              // Only PRs from last 7 days with no labels
+              if (createdAt < since || pr.labels.length > 0) {
+                continue;
+              }
+
+              const author = pr.user.login;
+              core.info(`Processing PR #${pr.number} by ${author}`);
+
+              let isFoundation = false;
+              let isDeveloper = false;
+
+              // Check foundationorg membership
+              try {
+                await github.rest.orgs.checkMembershipForUser({
+                  org: foundationOrg,
+                  username: author
+                });
+                isFoundation = true;
+              } catch (e) {
+                // not a member
+              }
+
+              // Check developersorg membership
+              try {
+                await github.rest.orgs.checkMembershipForUser({
+                  org: developersOrg,
+                  username: author
+                });
+                isDeveloper = true;
+              } catch (e) {
+                // not a member
+              }
+
+              let label;
+              if (isFoundation) {
+                label = "foundation";
+              } else if (isDeveloper) {
+                label = "plc";
+              } else {
+                label = "external";
+              }
+
+              core.info(`Assigning label '${label}' to PR #${pr.number}`);
+
+              await github.rest.issues.addLabels({
+                owner,
+                repo,
+                issue_number: pr.number,
+                labels: [label]
+              });
+            }