Allow notification of two reviewers being assigned to a PR and two issue assignees (#838)

This is a duplicate of certbot/certbot#10345 for this repo

Author: ohemorange

.github/workflows/assigned.yaml

@@ -3,9 +3,6 @@ name: Issue Assigned
 on:
   issues:
     types: [assigned]
-
-  pull_request_target:
-    types: [assigned]
 jobs:
   send-mattermost-message:
     runs-on: ubuntu-latest
@@ -14,4 +11,4 @@ jobs:
       with:
         MATTERMOST_WEBHOOK_URL: ${{ secrets.MATTERMOST_ASSIGN_WEBHOOK }}
         TEXT: >
-            ${{ github.event.issue.assignee.login || github.event.pull_request.assignee.login }} assigned to "${{ github.event.issue.title || github.event.pull_request.title }}": ${{ github.event.issue.html_url || github.event.pull_request.html_url }}
+            ${{ github.event.assignee.login }} assigned to "${{ github.event.issue.title }}": ${{ github.event.issue.html_url }}

.github/workflows/review_requested.yaml

@@ -0,0 +1,16 @@
+name: Review Requested
+
+on:
+  pull_request_target:
+    types: [review_requested]
+jobs:
+  send-mattermost-message:
+    # Don't notify for the interim step of certbot/eff-devs being assigned
+    if: ${{ github.event.requested_reviewer.login != ''}}
+    runs-on: ubuntu-latest
+    steps:
+    - uses: mattermost/action-mattermost-notify@master
+      with:
+        MATTERMOST_WEBHOOK_URL: ${{ secrets.MATTERMOST_ASSIGN_WEBHOOK }}
+        TEXT: >
+            Review requested from ${{ github.event.requested_reviewer.login }} for "${{ github.event.pull_request.title }}": ${{ github.event.pull_request.html_url }}