Introduce mapping with transformation function API

[pasindufernando1]

Purpose

Addresses :
wso2/product-ballerina-integrator#1084
wso2/product-ballerina-integrator#1098

[Copilot]

Pull Request Overview

Adds support for transformation functions in the data mapping functionality, which generates functions with expression bodies as opposed to custom functions with block bodies.

• Introduces a new API endpoint transformationFunction that creates functions with expression bodies (e.g., => 0 for int, => "" for string)
• Extends existing DataMapManager.genMappingFunction to support both custom functions and transformation functions based on a boolean flag
• Adds comprehensive test coverage for different data types including records, arrays, and primitives

Reviewed Changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
testng.xml	Registers new test class for transformation function testing
DataMappingTransformationFunctionTest.java	Main test class with test cases for various data type mappings
DataMapperTransformFunctionRequest.java	Request model for transformation function API
DataMapperService.java	Adds new transformationFunction endpoint
DataMapManager.java	Refactors function generation to support both custom and transformation functions
Test resources (*.json, *.bal)	Test configurations and source files for various mapping scenarios

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[KavinduZoysa]

@pasindufernando1 added a minor suggestion