add test_backend step to release self-hosted images

Author: emmaling27

.github/workflows/release_self_hosted_images.yml

@@ -34,3 +34,9 @@ jobs:
       contents: read
       packages: write
       id-token: write
+
+  test_backend:
+    needs: release_backend
+    uses: ./.github/workflows/test_self_hosted_backend.yml
+    with:
+      git_sha: ${{ github.sha }}

.github/workflows/test_self_hosted_backend.yml

@@ -1,6 +1,12 @@
 name: Test Self-Hosted Backend
 
 on:
+  workflow_call:
+    inputs:
+      git_sha:
+        description: "Git SHA for backend image tag to test"
+        type: string
+        required: true
   workflow_dispatch:
     inputs:
       git_sha: