title: Azure static web app environment variable
body: <p>I am trying to publish Gatsbyjs by Azure Static web app.
  I have a plugin (gatsby-source-contentful).</p>
  <p>I need to pass variables like:</p>
  <pre><code>{
        resolve: `gatsby-source-contentful`,
        options: {
          spaceId: process.env.CONTENTFUL_SPACE_ID,
          accessToken: process.env.CONTENTFUL_ACCESS_TOKEN,
        },
  },
  </code></pre>
  <p>Error:</p>
  <pre><code>Running 'npm run build'...
  
  
  &gt; gatsby-starter-default@0.1.0 build /github/workspace
  &gt; gatsby build
  
  success open and validate gatsby-configs - 0.021s
  error Invalid plugin options for &quot;gatsby-source-contentful&quot;:
  
  - &quot;accessToken&quot; is required
  - &quot;spaceId&quot; is required
  not finished load plugins - 0.905s
  </code></pre>
  <p>Where can I pass this?</p>
  <p>Thanks.</p>