feat(ssl): add support and tests for ClientSSLCertConfig.FromClientCertContent

[pjendrusik]

feat(ssl): add support and tests for ClientSSLCertConfig.FromClientCertContent

• Introduced FromClientCertContent to allow passing cert/key as strings
• Added tests for successful SSL handshake using certs loaded from resources
• Added test for invalid cert/key handling via env stream input

Passing the cert and key via environment variables lets you configure ClientSSLCertConfig.FromClientCertContent without writing files.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

:white_check_mark: 987Nabil
:x: pjendrusik
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[netlify[bot]]

✅ Deploy Preview for zio-http ready!

Name	Link
🔨 Latest commit	6c4d1d9b32a31f1766aa5948e113835460ad3253
🔍 Latest deploy log	https://app.netlify.com/projects/zio-http/deploys/6852bab350e583000866a849
😎 Deploy Preview	https://deploy-preview-3557--zio-http.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 project configuration.

[987Nabil]

@pjendrusik please check the build errors