Support AWS IAM Role Service Account

[Anhui-tqhuang]

Currently s3proxy has already supported azure default credentials through the following configurations

JCLOUDS_PROVIDER='azureblob-sdk'
JCLOUDS_ENDPOINT="https://tqupm45098.blob.core.windows.net"
JCLOUDS_IDENTITY=""
JCLOUDS_CREDENTIAL=""
AZURE_CLIENT_ID="xxx"
AZURE_TENANT_ID="xxx"
AZURE_CLIENT_SECRET="REDACTED"

Could we support aws iam role service account, so we could use the following configurations to auth:

JCLOUDS_PROVIDER='aws-s3'
JCLOUDS_ENDPOINT="https://MyBucket.ue-east-1.s3.amazonaws.com"
JCLOUDS_IDENTITY=""
JCLOUDS_CREDENTIAL=""
AWS_ROLE_ARN="arn:aws:iam::123456789012:role/MyRole"
AWS_WEB_IDENTITY_TOKEN_FILE="/var/run/secrets/eks.amazonaws.com/serviceaccount/token"

[gaul]

I don't have a specific answer to this but I believe that jclouds has some machinery to drive STS:

https://stackoverflow.com/questions/23520216/using-aws-s3-via-jclouds-how-to-assume-role

So this might just need to be configured on the S3Proxy side. Do you know Java and if so could you look into this?

Longer-term I would like to add an storage backend that uses the AWS SDK, similar to azureblob-sdk, but I won't have time to work on this for a while.

[Anhui-tqhuang]

sorry @gaul I am a golang developer, know nothing about JAVA 🤣

[gaul]

Fixed by #749.