Missing start boundary for multipart body

Q&A (please complete the following information)

• OS: Linux
• Browser: Chrome / Firefox
• Version: 105/104
• Method of installation: npm
• Swagger-UI version: using swagger-jaxrs2-jakarta/2.2.2
• OpenAPI version: OpenAPI 3.0

Content & configuration

Example Swagger/OpenAPI definition:

openapi: 3.0.3
info:
  title: FormData MultiPart Example
  version: 1.0.0
paths:
  /foo:
    post:
      operationId: updatePet
      parameters:
        - name: id
          in: query
          required: true
          schema:
            pattern: ^(?!aliases$)(?!ids$)[-_.a-zA-Z0-9]+$
            type: string
        - name: additionalMetadata
          in: query
          description: Additional Metadata
          required: false
          schema:
            type: string
      requestBody:
        content: 
          multipart/form-data: # Media type
            schema:   
              type: string
              format: binary
      responses:
        '200':
          description: Successful operation

Describe the bug you're encountering

It seems that there is no start boundary set. Chrome Dev Tools also only show the end boundary but no start boundary. This leads to the following exception on the server:

Caused by: org.jvnet.mimepull.MIMEParsingException: Missing start boundary
at org.jvnet.mimepull.MIMEParser.skipPreamble(MIMEParser.java:288)
at org.jvnet.mimepull.MIMEParser.access$300(MIMEParser.java:38)
at org.jvnet.mimepull.MIMEParser$MIMEEventIterator.next(MIMEParser.java:124)
at org.jvnet.mimepull.MIMEParser$MIMEEventIterator.next(MIMEParser.java:102)
at org.jvnet.mimepull.MIMEMessage.makeProgress(MIMEMessage.java:199)
at org.jvnet.mimepull.MIMEMessage.parseAll(MIMEMessage.java:160)
at org.jvnet.mimepull.MIMEMessage.getAttachments(MIMEMessage.java:86)

To reproduce...

Steps to reproduce the behavior:
Just fill out the form and have a look at the request header

Expected behavior

There should be a start boundary set, but there isn't any.

Screenshots

Additional context or thoughts

The curl command produced by swagger-ui works as expected, there the start boundary is set.

No source file or test is identified. Start with the provided OpenAPI multipart example and the browser request-generation path; compare the generated browser request with the working curl command. Done means the browser request includes a valid multipart start boundary and the server no longer reports a missing boundary.