Do not serialize scalar values

[richardhj]

I don't know why all properties are becoming json_encoded, but this resulted in properties having malicious characters (i.e., ") when using asText().

Example:

Before:

$page->getProperty('E-Mail-Adresse')->asText(); // "me@example.org"

After:

$page->getProperty('E-Mail-Adresse')->asText(); // me@example.org

[what-the-diff]

PR Summary

• Improved asText() method handling
  Added a condition to better handle different content types, improving overall functionality.

[johguentner]

Thank you @richardhj for the PR!
Yeah, this is a valid point! When I wrote the ->asText() method, I wasn't sure what to do with certain properties. For scalar values, this definitely makes sense!

Could you please write tests for the implementation. Then we will merge this within 1.1.0.