Created get_url methods for message, channel and user.

[ruslan-ilesik]

feat: allow get_url methods for message, channel and user or as (user_url , message_url, channel_url, thread_url) in dpp::utility namespace.

test: created unit tests for all this methods.

Introduced new constant to dpp::utility namespace, called url_host (in analogy to cdn_host)

• My pull request is made against the dev branch.
• I have ensured that the changed library can be built on your target system. I did not introduce any platform-specific code.
• I have ensured that all methods and functions are fully documented using doxygen style comments.
• I tested my commits, by adding a test case to the unit tests if needed
• I have ensured that I did not break any existing API calls.
• My code follows the coding style guide (if you are not sure, match the code style of existing files including indent style etc).
• I have not built my pull request using AI, a static analysis tool or similar without any human oversight. Where I have generated this pull request using a tool, I have justified why this is needed.

[netlify]

✅ Deploy Preview for dpp-dev ready!

Name	Link
🔨 Latest commit	ddb17ea
🔍 Latest deploy log	https://app.netlify.com/sites/dpp-dev/deploys/65048198eedc2900084104b7
😎 Deploy Preview	https://deploy-preview-855--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.

[CLAassistant]

All committers have signed the CLA.

[Commandserver]

Very nice too see this feature here!

[Mishura4]

Looks good to me!

doesn't seem to be a review?