deprecate edns methods, add extensions

[leshow]

Assuming we're still good to go ahead with this modification, for reference the workaround for not being able to remove EDNS, as best I can work out is:

fn remove_edns(msg: Message) -> Message {
    let rcode = msg.response_code();
    let MessageParts {
        header,
        queries,
        answers,
        name_servers,
        additionals,
        sig0,
        edns,
    } = msg.into_parts();

    let mut ret = Message::new();
    ret.set_id(header.id())
        .set_message_type(header.message_type())
        .set_op_code(header.op_code())
        .set_authoritative(header.authoritative())
        .set_truncated(header.truncated())
        .set_recursion_desired(header.recursion_desired())
        .set_recursion_available(header.recursion_available())
        .set_authentic_data(header.authentic_data())
        .set_checking_disabled(header.checking_disabled())
        .set_response_code(rcode)
        .add_queries(queries)
        .add_answers(answers)
        .add_name_servers(name_servers);
    ret.insert_additionals(additionals);

    for sig in sig0 {
        ret.add_sig0(sig);
    }
    ret
}

Looking at all this, a MessageBuilder could probably help make constructing new Messages lot nicer, happy to sketch that out on an issue or something if you like. Let me know if you want to remove the MessageParts -> Message bit from this also... I included it here but if we pursue a builder maybe it's not as necessary.

[leshow]

Woop, forgot to re-run the tests lol. doh

edit:
After messing around with all the call sites I'm less confident in making this change, going to play with a few things and I'll post again later.

[codecov]

Codecov Report

Merging #1675 (ad5b0c4) into main (f91b45f) will decrease coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1675      +/-   ##
==========================================
- Coverage   79.92%   79.87%   -0.05%     
==========================================
  Files         177      183       +6     
  Lines       18309    18597     +288     
==========================================
+ Hits        14632    14853     +221     
- Misses       3677     3744      +67     

[bluejekyll]

This looks good. See this comment: #1675 (comment)

I think once that is changed in terms of usage, this is good.

[bluejekyll]

Looks great. There's a minor unused error right now, this is ready once that's clean.

[leshow]

Let me know if you want an additional unit test or something to bump up the codecov

[bluejekyll]

Looks great. Thanks for fixing up this interface. And thanks for the PR.