This commit introduces the `request_specific_fields` option in OpenURI.
It provides two methods for customizing headers as follows.
1. Specify headers only for the initial request
Use a Hash to apply headers only to the first request.
These headers are automatically removed during redirects.
2. Specify headers dynamically for each request
Use a Proc to dynamically generate headers for each request,
including during redirects, based on the request URL.
This feature allows users to control headers flexibly,
ensuring that sensitive headers like "Authorization" are not unintentionally
transferred during redirects unless explicitly specified.
https://github.com/ruby/open-uri/commit/460f858e3c