feat: add imported DDB tables for gen 2 migration in experimental state

[dpilch]

Description of changes

Add feature to import DDB tables for gen 2 migration in experimental state.

• feat: set migrations to experimental #2998
• fix: allowlist comparison properties on imported table #2908
• test: add additional migration validation test cases #2792
• A few migration pr followups #2753
• Migration validation e2e #2752
• feat: add overrideIndexName to configure index name #2738
• fix: adjust default table properties #2726
• test: migration e2es #2703
• feat: validate imported tables #2696
• feat: get datasource map for migration #2668
• feat: import existing table to amplify managed table #2634
• feat: set migrations to experimental #2998
• fix: allowlist comparison properties on imported table #2908
• test: add additional migration validation test cases #2792

List of all PR to feature/gen2-migration:
https://github.com/aws-amplify/amplify-category-api/pulls?q=is%3Apr+is%3Aclosed+base%3Afeature%2Fgen2-migration+

Documentation has not been updated. This will be done with the official release of migrations.

CDK / CloudFormation Parameters Changed

• Add overrideIndexName to @belongsTo to change the name of the GSI that is automatically created with references.
• New data source strategy: IMPORTED_AMPLIFY_TABLE.
• New construct prop: importedAmplifyDynamoDBTableMap.

importedAmplifyDynamoDBTableMap will define a mapping of model name to imported table name. All models defined with the IMPORTED_AMPLIFY_TABLE should have a matching key in the importedAmplifyDynamoDBTableMap prop.

import * as cdk from "aws-cdk-lib";
import { Construct } from "constructs";
import {
  AmplifyGraphqlApi,
  AmplifyGraphqlDefinition,
} from "@aws-amplify/graphql-api-construct";
import * as path from "path";

export class BackendStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const amplifyApi = new AmplifyGraphqlApi(this, "MyNewApi", {
      definition: AmplifyGraphqlDefinition.combine([
        AmplifyGraphqlDefinition.fromString(
          `
            type Todo @model @auth(rules: [{ allow: public }]) {
              title: String
            }
          `,
          {
            dbType: "DYNAMODB",
            provisionStrategy: "DEFAULT",
          },
        ),
        AmplifyGraphqlDefinition.fromString(
          `
            type Blog @model @auth(rules: [{ allow: public }]) {
              title: String
              content: String
              authors: [String]
            }
          `,
          {
            dbType: "DYNAMODB",
            provisionStrategy: "IMPORTED_AMPLIFY_TABLE",
          },
        ),
      ]),
      importedAmplifyDynamoDBTableMap: {
        // existing table
        Blog: 'Blog-xxxx-NONE',
      },
      authorizationModes: {
        defaultAuthorizationMode: "API_KEY",
        apiKeyConfig: {
          expires: cdk.Duration.days(30),
        },
      },
    });
  }
}

Issue #, if available

N/A

Description of how you validated changes

• Unit tests
• E2E tests
  • PredictionsTransformerV2Tests.e2e.test.ts is passing locally

Checklist

• PR description included
• yarn test passes
• E2E test run linked
• Tests are changed or added
• New AWS SDK calls or CloudFormation actions have been added to relevant test and service IAM policies
• Any CDK or CloudFormation parameter changes are called out explicitly

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