Add a new workflow for release branch processing

.github/workflows/check-release-branches.yaml

@@ -0,0 +1,65 @@
+---
+name: Check release branches
+on:
+  push:
+      - "release/**"  # We should only react to branches like "release/networkservicemesh/*/v*.*.*"
+      - "!release/*"  # and ignore branches like "release/v*.*.*". "**" - any character, "*" - any character except "/"
+
+concurrency:
+  group: check-release-branches
+  cancel-in-progress: true
+
+jobs:
+  check-release-branches:
+    name: Check release branches
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+
+    - name: Set envs
+      run: |
+        echo "tag=$(echo ${{ github.event.ref }} | awk -F '/' '{print $NF}')" >> $GITHUB_ENV
+        {
+          echo 'branches<<EOF'
+          echo $(git branch -r | grep -e "release/networkservicemesh/.*/${{ env.tag }}")
+          echo EOF
+        } >> $GITHUB_ENV
+
+      # On this step we get all image names from deployments-k8s/apps folder and
+      # compare them to the set of release/networkservicemesh/cmd-*/${tag} branches.
+      # If the sets of branches and images are equal then we merge all
+      # release/networkservicemesh/cmd-*/${tag} branches into release/${tag} branch.
+    - name: Check release branches
+      run: |
+        images=$(grep -roh 'apps' -e "ghcr\.io\/networkservicemesh\/ci\/.*" | cut -d'/' -f4 | cut -d':' -f1 | sort -u)
+        branches=$(echo ${{ env.branches }} | tr ' ' '\n' | cut -d'/' -f4 | sort -u)
+        diff <(echo "$branches") <(echo "$images")
+
+    - name: Merge branches
+      run: |
+        git config --global user.email "nsmbot@networkservicmesh.io"
+        git config --global user.name "NSMBot"
+
+        git checkout -b release/${{ env.tag }}
+        for branch in ${{ env.branches }}; do
+          git merge $branch
+        done
+
+        git push -u origin release/${{ env.tag }}
+
+      # After merging all release branches we remove them from remote deployments-k8s
+    - name: Remove release branches
+      run: |
+        for branch in ${{ env.branches }}; do
+          branch=${branch#"origin/"}
+          gh api \
+            --method DELETE \
+            -H "Accept: application/vnd.github+json" \
+            -H "X-GitHub-Api-Version: 2022-11-28" \
+            /repos/networkservicemesh/deployments-k8s/git/refs/heads/$branch
+        done
+      env:
+        GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}