Boundaries for multipart requests in plain HTTP are incorrect

Describe the bug
Currently, the Code Generator for (plain) HTTP is using the same boundary everywhere instead of following the RFC. When trying to send the generated code through an HTTP client, e.g. in IntelliJ, the IDE will point out that the boundaries are incorrect, and the request will fail.

To Reproduce
Steps to reproduce the behavior:

• create a POST using a form-data body
• add a key "foo" and text value "bar"
• generate the HTTP code

Expected code snippet and corresponding request
The generated code is correct according to the definition of the aforementioned RFC which means:

• there is a boundary defined alongside Content-Type: multipart/form-data (let's say xyz)
• the boundary is used to separate different form data with two additional hyphens before (--xyz)
• the request ends with a boundary with two leading and trailing hyphens (--xyz--)

Screenshots
All boundaries are identical but should follow the rules above.

Additional context
Version of postman-code-generators/Postman app: 9.16.1

Start by reproducing the plain HTTP code generation for a POST with a form-data body containing the foo/bar field, then compare the generated multipart request with RFC 1341. Done means the Content-Type boundary is declared, each separator uses the boundary with two leading hyphens, and the closing delimiter has two leading and two trailing hyphens.