openapi3gen: Fix issue with separate component generated for time.Time

[d1vbyz3r0]

openapi3gen generates separate schema component for time.Time properies, when ExportComponentSchemas opt provided.
Here is a small example:

type Some struct {
	Name      string
	CreatedAt time.Time
}

func main() {
	schemas := make(openapi3.Schemas)
	g := openapi3gen.NewGenerator(
		openapi3gen.UseAllExportedFields(),
		openapi3gen.CreateComponentSchemas(openapi3gen.ExportComponentSchemasOptions{
			ExportComponentSchemas: true,
		}),
	)

	ref, err := g.NewSchemaRefForValue(&Some{}, schemas)
	if err != nil {
		panic(err)
	}

	schema, _ := json.MarshalIndent(ref, "", "  ")
	fmt.Println(string(schema))
}

Expected output is:

{
  "properties": {
    "CreatedAt": {
      "format": "date-time",
      "type": "string"
    },
    "Name": {
      "type": "string"
    }
  },
  "type": "object"
}

But for now generator produces following:

{
  "properties": {
    "CreatedAt": {
      "$ref": "#/components/schemas/Time"
    },
    "Name": {
      "type": "string"
    }
  },
  "type": "object"
}

[fenollp]

Please add your example as a test and we should be good to go.