title: Azure yaml pipeline using "extends"
body: <p>I am trying to use extends as part of my pipeline. I am trying to get the first basic step working from Azure docs ie</p>
  
  <pre><code>    # pythonparameter-template.yml
      parameters:
      - name: usersteps
        type: stepList
        default: []
      steps:
      - ${{ each step in parameters.usersteps }}
        - ${{ step }}
  
  # azure-pipelines.yml
  trigger: none
  
  resources:
    repositories:
    - repository: CI-CD-Templates
      type: git
      name: /CI-CD-Templates
      ref: refs/heads/master
  
  extends:
    template: /pythonparameter-template.yml@CI-CD-Templates
    parameters:
      usersteps:
      - script: echo This is my first step
      - script: echo This is my second step
  </code></pre>
  
  <p>I keep getting the below error:</p>
  
  <blockquote>
    <p>The directive 'each' is not allowed in this context. Directives are not supported for expressions that are embedded within a string. Directives are only supported when the entire value is an expression
    Unexpected value '${{ each step in parameters.usersteps }} - ${{ step }}'</p>
  </blockquote>
  
  <p>Also after I extend from a template can azure-pipelines.yml also have it's own custom steps ie</p>
  
  <pre><code># azure-pipelines.yml
  resources:
    repositories:
    - repository: templates
      type: git
      name: MyProject/MyTemplates
      ref: tags/v1
  
  extends:
    template: template.yml@templates
    parameters:
      usersteps:
      - script: echo This is my first step
      - script: echo This is my second step
  steps:
  - template: /validation-template.yml@CI-CD-Templates
   parameters:
    commitMessage: $(commitMessage)
  
  - template: /shared-template.yml@CI-CD-Templates
   parameters:
   buildArtifactDir: $(buildArtifactDir)
  </code></pre>