Add new Nuxeo AWS service to get credentials and other config

A new template aws is available, to define the AWS configuration. When activated (which is automatically done by the marketplace-amazon-s3 package), the following nuxeo.conf properties are available: nuxeo.aws.accessKeyId nuxeo.aws.secretKey nuxeo.aws.region They are optional, and if not present the default AWS SDK mechanism for configuring them will be used (environment variables, Java system properties, local AWS profile, container-specific configuration (ECS/EC2)). See https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/credentials.html#credentials-default and https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/java-dg-region-selection.html#default-region-provider-chain for more information. Instead of using the template, the service can also be configured manually: <extension target= "org.nuxeo.runtime.aws.AWSConfigurationService" point= "configuration" > <configuration> <accessKeyId> MY_ACCESS_KEY_ID </accessKeyId> <secretKey> MY_SECRET_KEY </secretKey> <region> MY_REGION </region> </configuration> </extension> From Java there are two new APIs to get this information: NuxeoAWSCredentialsProvider.getInstance() NuxeoAWSRegionProvider.getInstance().getRegion() These credentials and region providers will default to standard AWS SDK behavior if no Nuxeo configuration is provided (see above).