s3 Amazon's V4 authentication API compatible

[devansvd]

trafficstars

Currently proxy requests fails since amazon moved to v4 authentication api, This provides necessary changes as per instructions given in ngx_aws_auth to authenticated S3 backends using Amazon's V4 authentication API.

These are the new scopes added for V4 auth

    aws_access_key your_aws_access_key; # Example AKIDEXAMPLE
    aws_key_scope scope_of_generated_signing_key; #Example 20150830/us-east-1/service/aws4_request
    aws_signing_key signing_key_generated_using_script; #Example L4vRLWAO92X5L3Sqk5QydUSdB0nC9+1wfqLMOKLbRp4=
    aws_s3_bucket your_s3_bucket;

Script to generate aws_signing_key & aws_signing_key is copied from the ngx_aws_auth and included in this repo.

Note: aws_signing_key is rotated often looks like it expires within a week.