feat: add custom resource cdk stack parser and transformer

[sanjanaravikumar-az]

This PR introduces enhancements to the Amplify CLI Gen2 migration tooling, focusing on custom resource transformation capabilities.

Changes-

Scanner: Traverses the amplify/backend/custom/ directory to discover all custom resources and
locate their cdk-stack.ts files. It provides the initial inventory of resources that need to be
migrated from Gen1 to Gen2.

Parser: Uses TypeScript AST to analyze Gen1 CDK stack files and extract structured information
including imports, class names, constructor bodies, and outputs. It also detects specific Gen1
patterns like CfnParameters, AmplifyHelpers calls, and CDK function references that require
transformation.

Transformer: Converts Gen1 code patterns to Gen2 equivalents using a hybrid approach of TypeScript
AST manipulation and string replacement fallbacks. It handles complex transformations like replacing
cdk.Fn.ref('env') with process.env.AMPLIFY_ENV and AmplifyHelpers.getProjectInfo() with environment
variable access.

Generator: Creates Gen2-compatible resource.ts files and backend integration code from the
transformed data. It filters out Gen1-specific imports, adds required Gen2 imports like constructs,
and generates proper class structures with backend.ts integration code.

Unit Tests:

• Scanner: Custom resource discovery and file system operations

• Parser: CDK pattern detection and AST analysis

• Transformer: AST and string-based code transformations

• Generator: Gen2 file generation and backend integration

• PR description included

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

To fix the problem, remove the unused variable declaration.
Specifically, delete the line:

const patterns = this.patternDetector.detectPatterns(parsed.constructorBody);

found on line 39 in packages/amplify-cli/src/commands/gen2-migration/codegen-custom-resources/index.ts.
No other code depends on this variable, so its removal will not affect functionality.
No imports nor method definitions need adjustment, as only a single line should be removed.

---

To resolve the issue, we should remove the unused import statement import * as fs from 'fs-extra'; from the top of the file. This change is limited to a single line at the start of the file and will not affect any functionality since fs from fs-extra is not referenced anywhere in this file. No other code changes or dependency adjustments are needed.