Use string views

[BowDown097]

This will make the library easier to use for std::string_view users as a LOT of explicit std::string creations are needed atm. There should be some performance improvements as well (less allocations, blablabla). Tested with my own bot which is pretty complex and works 100%.

This is completely backwards compatible in my testing, with the exception of implicit conversions. For example, within the library itself, there were some assignments of a utility::icon to a string that would implicitly create a utility::iconhash - now it does not, and does not compile without explicitly creating the iconhash. With my own bot this happened with std::smatch.

There's also some new stuff / changes outside of just changing std::strings to std::string_views:

• A new utility function for maps, dpp::utility::emplace_or_assign, which essentially is insert_or_assign but with the in-place construction that emplace offers.
• All non-floating point instances of std::stoX that would take in a std::string_view have been changed to use std::from_chars.
• 2 new types, dpp::membuf and dpp::imemstream, in stringops.h, which allow input streams over a raw character array, necessary for std::string_view. These are not compiled if std::ispanstream is available, which was added in C++23, as it is far superior. All instances of std::istringstream that would take in a std::string_view have been replaced to use one or the other, depending on what's available. (P.S. should these be exported with DPP_EXPORT?)

Code change checklist

• [x] I have ensured that all methods and functions are fully documented using doxygen style comments.
• [x] My code follows the coding style guide.
• [x] I tested that my change works before raising the PR.
• [x] I have ensured that I did not break any existing API calls.
• [x] I have not built my pull request using AI, a static analysis tool or similar without any human oversight.

[netlify[bot]]

✅ Deploy Preview for dpp-dev ready!

Name	Link
🔨 Latest commit	803ba5374ba212cef2e9036729e4ee0355b229f7
🔍 Latest deploy log	https://app.netlify.com/sites/dpp-dev/deploys/66753a30bc972b0008214fc0
😎 Deploy Preview	https://deploy-preview-1177--dpp-dev.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[braindigitalis]

I'm not sure why every instance of a string parameter, plus various strings in objects must all be changed to string views. this is a huge change which is impossible to review and impossible to say what side effects it has as it changes literally every function. how can we say this doesn't break things, the unit tests or one test bot don't scratch the surface for such a far reaching change.

it's better to concentrate on one subsystem at a time doing a gradual refactor than what looks like global search and replace.

string view is not a magic bullet.

[BowDown097]

Yeah, good points. I had an initial idea for this which is probably better and that I'll do instead.