fix(execute): fix encoding for stringified request body

[glowcloud]

Refs swagger-api/swagger-ui#7810

With these changes we should now parse the string and then iterate through it only if it's actually an object.

The issue is that we are sending a stringified object and then iterating through it as if it were just an object. It happened even if I updated the examples in the specification provided in the issue, which seemed wronged to me, to:

examples:
  authorization_code grant type:
    description: authorization_code grant type
    value:
      grant_type: authorization_code
      code: xxxxxxxxxx
      client_id: xxxxxxxxxx
  client_credentials grant type:
    description: client_credentials grant type
    value: 
      grant_type: client_credentials
      client_id: xxxxxxxxxx
      client_secret: xxxxxxxxxx
  refresh_token grant type:
    description: refresh_token grant type
    value: 
      grant_type: refresh_token
      refresh_token: xxxxxxxxxx

so that it shows as an object in Swagger UI:

[swagger-bot]

🎉 This PR is included in version 3.27.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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