V2: unable to produce string binary request body

[zak905]

Describe the bug

According to the OpenAPI 3 documentation https://swagger.io/docs/specification/v3_0/describing-request-body/file-upload/, it is possible to specify a binary file request body by specifying the type as string and the format as binary. For example:

requestBody:
  content:
    image/png:
      schema:
        type: string
        format: binary

This is somehow different from swagger 2 format which needs the usage of formData for specifying binary data

      parameters:
      - description: 'file binary data'
        in: formData
        name: payload
        required: true
        type: file

Not only the annotation for specifying a binary data file did not change from version 1 to version 2 of swag:

// @Accept  application/octet-stream
// @Param payload formData file true "file binary data"

but also the produced specs are confusing if I use --v3.1:

 operationId: test-post
      requestBody:
        content:
          application/octet-stream:
            schema:
              format: binary
              type: string
          application/x-www-form-urlencoded:
            schema:
              type: file
        description: 'file binary data'
        required: true

I am not sure why the application/x-www-form-urlencoded is part of generated of the specs. I believe it's more accurate to have only the type specified by @Accept in addition to format: binary for the definition:

     operationId: test-post
      requestBody:
        content:
          application/octet-stream:
            schema:
              format: binary
              type: string
        description: 'file binary data'
        required: true

It would help if a new annotation is added for v2 that will help in producing definitions for binary types. For example:

// @Accept  application/octet-stream
// @Param payload binary file true "file binary data"

To Reproduce
running swag init --v3.1 on a folder that contains the following file:

package main

import "fmt"

//	@title			Swagger Example API
//	@version		1.0
//	@description	This is a sample server Petstore server.
//	@termsOfService	http://swagger.io/terms/

//	@contact.name	API Support
//	@contact.url	http://www.swagger.io/support
//	@contact.email	[email protected]

//	@license.name	Apache 2.0
//	@license.url	http://www.apache.org/licenses/LICENSE-2.0.html

// @servers.url		https://petstore.swagger.io/v2
func main() {
	fmt.Println("testing")
}

// @ID test-post
// @Param payload formData file true "file binary data, acceptable formats: jpeg,png"
// @Accept  application/octet-stream
// @Produce octet-stream
// @Success 200 {file} file "response contains the file"
// @Router /test [post]
func getFile() {
	fmt.Println("test")
}

Expected behavior

     operationId: test-post
      requestBody:
        content:
          application/octet-stream:
            schema:
              format: binary
              type: string
        description: 'file binary data'
        required: true

Your swag version
v2.0.0

Your go version
1.22.4