Endpoint API: Endpoint#outCodec Doesn't Respect The Specified HeaderCodec

[khajavi]

Describe the bug
In the following example I expect the Endpoint API, to respect the header codec HeaderCodec.contentType.expect(Header.ContentType(MediaType.multipart.mixed/)) so the content type of the response should be multipart/mixed but the current content type returned by this route is multipart/form-data

To Reproduce
Steps to reproduce the behavior:

run the following example:

import zio._
import zio.http._
import zio.http.codec._
import zio.http.endpoint.Endpoint
import zio.http.endpoint.EndpointMiddleware.None
import zio.schema.DeriveSchema.gen
import zio.schema._
import zio.stream.ZStream

case class Book(title: String, authors: List[String])
object Book {
  implicit val schema = DeriveSchema.gen[Book]
}

object EndpointExample extends ZIOAppDefault {
  val endpoint: Endpoint[Int, Int, ZNothing, (Book, ZStream[Any, Nothing, Byte]), None] =
    Endpoint(RoutePattern.GET / "books" / PathCodec.int("id"))
      .outCodec(
        HttpCodec.content[Book]("book", MediaType.application.`json`) ++
          HttpCodec.binaryStream("file", MediaType.application.`octet-stream`) ++
          HeaderCodec.contentType.expect(Header.ContentType(MediaType.multipart.`mixed`)),
      )

  def run = Server
    .serve(
      endpoint
        .implement(handler { (id: Int) =>
          (Book("John's Book", List("John Doe")), ZStream.from(Chunk.fromArray("the book file".getBytes)))
        })
        .toHttpApp @@ Middleware.debug,
    )
    .provide(Server.default, Scope.default)
}

Then run the following curl command:

curl -X GET 'http://127.0.0.1:8080/books/123' -i

Expected behavior

HTTP/1.1 200 OK
content-type: multipart/mixed
transfer-encoding: chunked

------zio-http-boundary-D4792A5C-93E0-43B5-9A1F-48E38FDE5714
Content-Disposition: form-data; name="book"
Content-Type: application/json

{"title":"John's Book","authors":["John Doe"]}
------zio-http-boundary-D4792A5C-93E0-43B5-9A1F-48E38FDE5714
Content-Disposition: form-data; name="file"
Content-Type: application/octet-stream

the book file
------zio-http-boundary-D4792A5C-93E0-43B5-9A1F-48E38FDE5714--

[jdegoes]

/bounty $150

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Attempt	Started (GMT+0)	Solution
🟢 @987Nabil		#2896

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