ci: fix feature branch deployment pipeline (#292)

## Description:
- resolve nested templates to prevent empty variables
- add code comments

.azuredevops/pipelines/deploy-to-cdn.yml

@@ -73,10 +73,17 @@ steps:
       - bash: |
           echo "$(branch)"
         displayName: 'Log normalized branch name'
+      ## Push to CDN feature branch folder
       - template: templates/push-to-storage-feature.template.yml
+      ## Purge CDN for branch folder
+      - template: purge-feature-cdn.template.yml
 
   - ${{ if eq(variables['Build.SourceBranch'], 'refs/heads/main') }}:
+      ## Push to CDN version folders
       - template: templates/push-to-storage-main.template.yml
+      ## Purge CDN for all version folders
+      - template: purge-main-cdn.template.yml
+
       ## If deployment variable is set to 'none' do nothing
       - script: |
           if [[ $(deployment) == "code" ]]; then

.azuredevops/pipelines/templates/push-to-storage-feature.template.yml

@@ -7,7 +7,7 @@ steps:
       scriptType: 'bash'
       scriptLocation: 'inlineScript'
       inlineScript: |
-        # Deploy to version folder
+        # Deploy to branch folder
         set -x
         echo "Target folder is $(branch)"
         az storage blob upload-batch \
@@ -17,6 +17,3 @@ steps:
           --destination-path "/$(branch)" \
           --overwrite
         set +x
-
-    ## Purge CDN for branch folder
-  - template: purge-feature-cdn.template.yml

.azuredevops/pipelines/templates/push-to-storage-main.template.yml

@@ -99,6 +99,3 @@ steps:
         else
           echo "Deployment type is 'none', therefore nothing to deploy."
         fi
-
-  ## Purge CDN for all folders
-  - template: purge-main-cdn.template.yml