Add instructions on how to update notify_teams assignees

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

.github/actions/notify_teams/README.md

@@ -0,0 +1,27 @@
+# notify Teams action
+
+This action is used to send a message to our Teams channel in case of a failure in the CI/CD pipeline.
+The action will automatically choose an engineer to assign to the issue and tag them in the message.
+
+Engineers are identified by their GitHub username and bound to a Microsoft Teams ID in `.attachments[0].content.msteams.entities`.
+To add a new engineer, add a new entry to the entity list in the format:
+
+```json
+{
+  "type": "mention",
+  "text": "${github_username}",
+  "mentioned": {
+    "id": "${msteams_id}",
+    "name": "${name}"
+  }
+}
+```
+
+Where `${github_username}` is the GitHub username of the engineer, `${msteams_id}` is the Microsoft Teams ID of the engineer, and `${name}` is the name of the engineer.
+To find the Microsoft Teams ID use the following command:
+
+```bash
+az ad user show --id ${email} --query id
+```
+
+Where `${email}` is the email address of the engineer.

.github/actions/notify_teams/action.yml

@@ -25,7 +25,7 @@ runs:
       continue-on-error: true
       shell: bash
       run: |
-        cp .github/teams_payload_template.json teams_payload.json
+        cp .github/actions/notify_teams/teams_payload_template.json teams_payload.json
 
         # Add workflow name to the notification
         yq -oj -iP '.attachments[0].content.body[0].columns[1].items[0].text = "${{ inputs.title }}"' teams_payload.json