Description of problem:

fetch:body and validate:body currently accept template units ($$...) but do not evaluate JSONata expressions inside the body. As a result, JSONata-based dynamic values in request bodies are not resolved. We need to support JSONata evaluation for both validation calls (validate:body) and data fetch calls (fetch:body), so schema authors can build request payloads dynamically from form data and responses.

Prerequisites (if any, like setup, operators/versions):

Steps to Reproduce

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Actual results:

JSONata expressions included in fetch:body or validate:body are not evaluated and are sent as literal strings.

Expected results:

JSONata expressions in fetch:body and validate:body are evaluated before the request is sent, for both fetch and validation calls.

Reproducibility (Always/Intermittent/Only Once):

Build Details:

Additional info (Such as Logs, Screenshots, etc):