[skipci] multinode: connect using github ssh key

add a checkbox to the stackhpc-multinode workflow to use the user's
ssh key registered in github instead of always copy-pasting

Author: elelaysh

.github/workflows/stackhpc-multinode.yml

@@ -46,8 +46,12 @@ name: Multinode
         description: How long to break execution for (minutes) (note that instances are cleaned up after 12h)
         type: number
         default: 60
+      use_my_ssh_key:
+        description: authorise my github ssh keys on Ansible control host
+        default: 'false'
+        type: boolean
       ssh_key:
-        description: SSH public key to authorise on Ansible control host
+        description: SSH public key to authorise on Ansible control host (if different from github ssh keys)
         type: string
       terraform_kayobe_multinode_version:
         description: terraform-kayobe-multinode version
@@ -58,9 +62,34 @@ name: Multinode
         default: 'false'
         type: boolean
 jobs:
+  github_user_ssh_keys:
+    name: Retrieve actor github ssh keys
+    runs-on: ubuntu-latest
+    # Map a step output to a job output, this allows other jobs to be gated on the filter results
+    outputs:
+        ssh_keys: ${{ steps.compute_ssh_keys.outputs.ssh_keys }}
+    steps:
+      - name: Retrieve github user ssh keys or use provided ones
+        id: compute_ssh_keys
+        run: |
+          # encode array using jq: https://jstrieb.github.io/posts/github-actions-multiline-outputs/
+          if ${{ inputs.use_my_ssh_key }} && [ -z "${{ inputs.ssh_key }}" ]; then
+            echo "Fetching ssh keys for ${{ github.actor }}"
+            ssh_keys="$(gh api /users/${{ github.actor }}/keys --jq '[.[].key]' | jq --compact-output)"
+            if [ -z "${ssh_keys}" ]; then
+              echo "E: Unable to get '${GITHUB_USER}' ssh keys (quotes added for clarity)"
+              exit 1
+          elif [ -n "${{ inputs.ssh_key }}" ]; then
+            # single string to JSON array
+            ssh_keys="$(jq --raw-input --slurp --compact-output '.|[.]' <<<"${{ inputs.ssh_key }}")"
+          else
+            ssh_keys=''
+          fi
+          echo "ssh_keys=${ssh_keys}" >> $GITHUB_OUTPUT;
   multinode:
     name: Multinode
-    uses: stackhpc/stackhpc-openstack-gh-workflows/.github/workflows/multinode.yml@1.4.1
+    needs: github_user_ssh_keys
+    uses: stackhpc/stackhpc-openstack-gh-workflows/.github/workflows/multinode.yml@multi_ssh_keys
     with:
       multinode_name: ${{ inputs.multinode_name }}
       os_distribution: ${{ inputs.os_distribution }}
@@ -71,7 +100,7 @@ jobs:
       break_on: ${{ inputs.break_on }}
       # Workaround loss of number type using fromJSON: https://github.com/orgs/community/discussions/67182
       break_duration: ${{ fromJSON(inputs.break_duration) }}
-      ssh_key: ${{ inputs.ssh_key }}
+      ssh_keys: ${{ github_user_ssh_keys.outputs.ssh_keys }}
       stackhpc_kayobe_config_version: ${{ github.ref_name }}
       # NOTE(upgrade): Reference the PREVIOUS and CURRENT releases here.
       stackhpc_kayobe_config_previous_version: ${{ inputs.upgrade == 'major' && 'stackhpc/2024.1' || 'stackhpc/2025.1' }}