ability to group function with custom stack

[ykethan]

Environment information

System:
  OS: macOS 15.2
  CPU: (8) arm64 Apple M1
  Memory: 251.27 MB / 16.00 GB
  Shell: /bin/zsh
Binaries:
  Node: 20.18.1 - ~/.nvm/versions/node/v20.18.1/bin/node
  Yarn: 1.22.22 - /opt/homebrew/bin/yarn
  npm: 10.8.2 - ~/.nvm/versions/node/v20.18.1/bin/npm
  pnpm: 9.15.2 - ~/Library/pnpm/pnpm
NPM Packages:
  @aws-amplify/auth-construct: 1.6.0
  @aws-amplify/backend: 1.14.0
  @aws-amplify/backend-auth: 1.5.0
  @aws-amplify/backend-cli: 1.4.8
  @aws-amplify/backend-data: 1.4.0
  @aws-amplify/backend-deployer: 1.1.15
  @aws-amplify/backend-function: 1.12.1
  @aws-amplify/backend-output-schemas: 1.4.0
  @aws-amplify/backend-output-storage: 1.1.4
  @aws-amplify/backend-secret: 1.1.5
  @aws-amplify/backend-storage: 1.2.4
  @aws-amplify/cli-core: 1.2.3
  @aws-amplify/client-config: 1.5.5
  @aws-amplify/deployed-backend-client: 1.5.0
  @aws-amplify/form-generator: 1.0.3
  @aws-amplify/model-generator: 1.0.12
  @aws-amplify/platform-core: 1.6.0
  @aws-amplify/plugin-types: 1.8.0
  @aws-amplify/sandbox: 1.2.10
  @aws-amplify/schema-generator: 1.2.7
  aws-amplify: 6.12.1
  aws-cdk: 2.176.0
  aws-cdk-lib: 2.176.0
  typescript: 5.7.3
No AWS environment variables
No CDK environment variables

Describe the feature

When assigning to custom resourceGroupName on a function and backend.ts contains the following

// function
defineFunction({
  name: "apifunction",
  entry: "./handler.ts",
  resourceGroupName: "api-stack",
});

// backend.ts
const apiStack = backend.createStack("api-stack");

this will throw Custom stack named api-stack has already been created

would be great if a custom stack is present the function does not create a new stack rather append to the existing stack

Use case

Would provide the ability to group lambda functions that interact with custom resources

[ykethan]

closing this issue as we can pass custom resourceGroupName on the function and add the custom api resources to this stack
using backend.apiFunction.stack