* Sample to provide a ExpressionDescriptorProvider
* fix variable accessor in VariableExpressionHandler
* remove Variable Expression to use default one
* Change the Variable Expression Provider to handle Variable Expression correctly
* need to check on UI Side and Server side is valid JSON is sent. For example, if a use change from a literal value to a Variable value, the value is sent to the API and result in an exception, we cannot handle invalid json without using Try/Catch
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Co-authored-by: Jérémie DEVILLARD <jdevillard@users.noreply.github.com>
Co-authored-by: Sipke Schoorstra <sipkeschoorstra@outlook.com>
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