Incorrect OpenAPI Generation with -NoDefaultResponses Parameter

[mdaneri]

Describe the Bug

When Enable-PodeOpenAPI is invoked using the -NoDefaultResponses parameter and an OpenAPI path is created without adding a response, the generated OpenAPI specification is not correct.

Steps To Reproduce

1. Run the following PowerShell commands:

   Enable-PodeOpenApi -Path '/docs/openapi' -OpenApiVersion '3.0.3' -DisableMinimalDefinitions -NoDefaultResponses
   
   Add-PodeRoute -Method 'Get' -Path '/hello' -ScriptBlock {
       Write-PodeJsonResponse -Value @{'message' = 'Hello!'} -StatusCode 200
   } -PassThru | Set-PodeOARouteInfo -Summary 'Hello from the server'

2. This generates the following OpenAPI YAML:

   /hello: 
     get: 
       summary: Hello from the server
       responses: []

This output is not compliant with the OpenAPI specification.

Expected Behavior

If no response is added, a default response should be automatically added. The corrected OpenAPI YAML should look like this:

/hello: 
  get: 
    summary: Hello from the server
    responses: 
      default: 
        description: No description

Fix

Automatically add a default response when no responses are specified to ensure compliance with the OpenAPI specification.