Fix cross-account deploys restricted by externalId

[g-andrade]

Issue

It's possible to restrict cross-account deploys to a specific externalId in IAM role policies.

Up until the present fix, however, such deploys with a custom externalId fail with HTTP 403 forbidden; removing the restriction from the IAM policy instantly allows for the deploy to happen.

My understanding of what's happening is:

1. a new AWSCodeDeployPublisher instance receives the externalId through its constructor and saves it:
   

   aws-codedeploy-plugin/src/main/java/com/amazonaws/codedeploy/AWSCodeDeployPublisher.java

   Lines 108 to 130 in 40d7b24

   	public AWSCodeDeployPublisher(
   	String s3bucket,
   	String s3prefix,
   	String applicationName,
   	String deploymentGroupName,
   	String deploymentConfig,
   	String region,
   	Boolean deploymentGroupAppspec,
   	Boolean waitForCompletion,
   	Long pollingTimeoutSec,
   	Long pollingFreqSec,
   	String credentials,
   	String awsAccessKey,
   	String awsSecretKey,
   	String iamRoleArn,
   	String externalId,
   	String includes,
   	String proxyHost,
   	int proxyPort,
   	String excludes,
   	String subdirectory) {
   	this.externalId = externalId;

2. when using "iamRoleArn" as credentials, the instance will retrieve externalId from the descriptor:
   

   aws-codedeploy-plugin/src/main/java/com/amazonaws/codedeploy/AWSCodeDeployPublisher.java

   Lines 204 to 207 in 40d7b24

   	aws = AWSClients.fromIAMRole(
   	this.region,
   	this.iamRoleArn,
   	this.getDescriptor().getExternalId(),

3. but the descriptor instance initializes its own externalId randomly:
   

   aws-codedeploy-plugin/src/main/java/com/amazonaws/codedeploy/AWSCodeDeployPublisher.java

   Lines 460 to 464 in 40d7b24

   	public DescriptorImpl() {
   	load();
   	if (externalId == null) {
   	setExternalId(UUID.randomUUID().toString());

Description of changes

Functional:

• use AWSCodeDeployPublisher.externalId instead of the descriptor's

Tooling-related:

• support building with recent versions of maven (HTTPS-less HTTP mirrors are now blocked)[*]
• fix Javadoc generation in Java 17 (it broke the build)

[*] closes #107, #115 and #116

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