问为什么代码线需要KMS键？

EN

const adminPipeline = new codepipeline.Pipeline(this, 'mynaviPipeline', {
  pipelineName: 'cdk-mynavi-pl',
});


const mynavi_cc_repo_name = 'cdk-mynavi-cc'
const mynavi_cc_repo = new codecommit.Repository(this,
  "mynavi-cc-repo",{
    repositoryName: mynavi_cc_repo_name,
    description:"for resizer repo"
})

const adminBuildProject = new codebuild.PipelineProject(this, 'adminBuildproject', {
  environment: {
    buildImage:codebuild.LinuxBuildImage.STANDARD_4_0,
    privileged:true, 
  },
  buildSpec: codebuild.BuildSpec.fromSourceFilename("./buildspec.yml")
});
const adminSourceOutput = new codepipeline.Artifact();
const adminSourceAction = new cdk.aws_codepipeline_actions.CodeCommitSourceAction({
  actionName: 'AdminSource',
  repository: mynavi_cc_repo,
  output: adminSourceOutput,
  trigger:  cdk.aws_codepipeline_actions.CodeCommitTrigger.POLL,
})

const dockerHubSecretArn = 'arn:aws:secretsmanager:ap-northeast-1:678100228231:secret:docker_login-TBFA5B';
const dockerHubSecret = secretsmanager.Secret.fromSecretCompleteArn(this, 'SecretFromCompleteArn', dockerHubSecretArn);

dockerHubSecret.grantRead(adminBuildProject)

cronEcrRepo.grantPullPush(adminBuildProject)
djangoEcrRepo.grantPullPush(adminBuildProject)
nginxEcrRepo.grantPullPush(adminBuildProject)

const adminBuildOutput = new codepipeline.Artifact();
const adminBuildAction = new cdk.aws_codepipeline_actions.CodeBuildAction({
  actionName: 'AdminCodeBuild',
  project: adminBuildProject,
  input: adminSourceOutput,
  outputs: [adminBuildOutput]
});

adminPipeline.addStage({
  stageName: "mynaviSource",
  actions: [adminSourceAction],
});
adminPipeline.addStage({
  stageName : "mynaviBuild",
  actions: [adminBuildAction]
});