[Feature Request]: Improve validation error messages during pipeline deployment

Issue: Validation Error Message is Not Informative (During Deploy)

Description

When attempting to deploy a pipeline, a validation error may occur. However, the system only displays a generic message:

Validation error  
Validation failed

This message does not provide sufficient detail to identify the root cause of the issue, making debugging difficult.

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Steps to Reproduce

1. Open Transform and Validate in the pipeline.
2. Configure transformation logic and input data.
3. Click Deploy.
4. Observe the error message when validation fails.

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Expected Behavior

The validation error message should be descriptive and actionable, especially during deployment. It should include:

• The specific field or configuration causing the error
• The reason for failure (e.g., invalid syntax, missing field, type mismatch)
• (Optional) Suggested fix or guidance

Example:

Validation error:
- Field `key.expression` is invalid
- Reason: JMESPath expression failed to evaluate (missing field `customer_id`)

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Actual Behavior

During deployment, only a generic error message is shown:

Validation error  
Validation failed

No additional context or debugging information is provided.

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Impact

• Makes deployment troubleshooting difficult
• Increases time spent identifying configuration issues
• Leads to trial-and-error debugging
• Degrades developer experience

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Suggested Improvement

Enhance validation error reporting during deployment by:

• Providing structured error details (field path + error message)
• Explaining the root cause clearly
• Including optional hints or links to documentation

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Additional Context

This issue is particularly problematic when working with:

• JMESPath expressions
• Complex transformation logic
• Nested configurations in pipeline setup

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Summary

Validation errors during deployment should provide clear and actionable feedback instead of generic messages. Improving this will significantly enhance usability and efficiency.

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Thanks!

Start by reproducing the failure through the Transform and Validate flow and inspect the deployment validation response that produces the generic message. Trace where that response is rendered during Deploy; done means field-level, actionable validation details are shown for the reported failure cases.