title: Serverless get SSM parameter by hierarchy path
body: <p>is there a way to retrieve multiple ssm parameters through serverless.yml into an environment variable?</p>
  <p>for example right now i have the parameters: &quot;/dev/db/user&quot; and &quot;/dev/db/password&quot; and on serverless.yml:</p>
  <pre><code>environment:
    DB_USER: ${ssm:/${self:custom.stage}/db/user}
    DB_PASSWORD: ${ssm:/${self:custom.stage}/db/password}
  </code></pre>
  <p>where custom.stage will be dev/prod etc.</p>
  <p>problem is there will be more db info, hostname, port maybe more who knows, so is there a way to retrieve everything into a single environment variable?</p>
  <p>i thought about using a single ssm parameter with a json string with all the info and parse it in the cloud function, but maybe there is something more like the aws cli command:
  <code>aws ssm get-parameters-by-path --path &quot;/dev/db&quot;</code> that is exactly what i need but for serverless</p>