feat: add functions to return the list of headers and their contents

[nponsard]

This PR adds a function to get a reference to the list of the headers stored in the Response.

Fixes #655.

Let me know if you have any remarks.

I was also thinking about having a function return a map where the index is the name of the header, but with this PR it can be easily done afterwards (outside of this library).

[johan-bjareholt]

@nponsard Considering the following change, I assume that this PR is not relevant anymore? 4ddcc3a

[nponsard]

Ah yes, this commit breaks what I've done.

It would be easy to make the Header struct public again, but that depends on the objectives of this project / what the maintainers want.

[algesten]

Headers in ureq public API are &str for both key and value. The Header struct is internal and I don't think we should make it public here, because if it's public in one part of the API, why isn't it used everywhere?

• https://docs.rs/ureq/latest/ureq/struct.Response.html#method.header
• https://docs.rs/ureq/latest/ureq/struct.Request.html#method.set

The variant of this PR I would consider would be headers() -> (String, String) (or maybe header_iter() -> impl Iterator<Item = (&str, &str)> if we want to avoid allocation)

[nponsard]

Headers in ureq public API are &str for both key and value. The Header struct is internal and I don't think we should make it public here, because if it's public in one part of the API, why isn't it used everywhere?

* https://docs.rs/ureq/latest/ureq/struct.Response.html#method.header

* https://docs.rs/ureq/latest/ureq/struct.Request.html#method.set

The variant of this PR I would consider would be headers() -> (String, String) (or maybe header_iter() -> impl Iterator<Item = (&str, &str)> if we want to avoid allocation)

Hello !
I changed the content of my commit to account for these design decisions :

• headers() -> (String, Option<String>)
• headers_iter() -> impl Iterator<Item = (&str, Option<&str>)>
• headers_hasmap() -> HashMap(String, Option<String>)

I'm not sure if the last one is useful here since it could be implemented by the user using headers_iter(). I can remove it if you want.

[algesten]

Closing since we are moving to 3.x. The HTTP crate API will have the functions required.