fix(object): mc: change generated Signature Version from v2 to v4

[gmile]

Before this change, using "mc" to generate a pre-sign URL using for uploading an object would not work. After manually updating the config from S3v2 to S3v4 all good now.

Command I used is:

mc share upload scaleway/my-bucket/test.png

Before the change it would generate a URL like this, and it doesn't work:

$ mc share upload scaleway/my-test-bucket/test.png
URL: https://s3.fr-par.scw.cloud/my-test-bucket/test.png
Expire: 7 days 0 hours 0 minutes 0 seconds
Share: curl https://s3.fr-par.scw.cloud/my-test-bucket/ -F signature=jE27Ptr/IkDJcP60ZqA7jJD7RnE= -F bucket=my-test-bucket -F policy=eyJleHBpcmF0aW9uIjoiMxAyMC0xMS0xOVQxMTo0OTo1Mi4xMloi2CJjb25kaXRpb25zIjpbWyJlcSIsIiRidWNrZXQiLCJkYW5sb24tc3RhZ2luZy1sb2dvLXVwbG9hZHMiXSxbImVxIiwiJGtleSIsInRlc3QucG5nIl1dfQ== -F AWSAccessKeyId=SCW3BBT57A1CZEXJD2T5 -F key=test.png -F file=@<FILE>
$

After the change it would generate a URL like this, and it works:

$ mc share upload scaleway/my-test-bucket/test.png
URL: https://s3.fr-par.scw.cloud/my-test-bucket/test.png
Expire: 7 days 0 hours 0 minutes 0 seconds
Share: curl https://s3.fr-par.scw.cloud/my-test-bucket/ -F bucket=my-test-bucket -F policy=eyJleHBpcmF0aW9uIjoiMjAyMC0xMS0xOVQxMTo1MzowMC42NzJaIiwiY29uZGl0aW9ucyI6W1siZXEiLCIkYnVja2V0IiwiZGFubG9uLXN0YWdpbmctbG9nby11cGxvYWRzIl0sWyJlcSIsIiRrZXkiLCJ0ZXN0LnBuZyJdLFsiZXEiLCIkeC1hbXotZGF0ZSIsIjIwMjAxMTEyVDxxNTMwMVoiXSxbImVxIiwiJHgtYW16LWFsZ29yaXRobSIsIkFXUzQtSE1BQy1TSEEyNTYiXSxbImVxIiwiJHgtYW16LWNyZWRlbnRpYWwiLCJTQ1dOQkJUNTdBRUNaRVhKRDJUWi8yMDIwMTExMi9mci1wYXIvczMvYXdzNF9yZXF1ZXN0Il1dfQ== -F x-amz-algorithm=AWS4-HMAC-SHA256 -F x-amz-credential=SCWXBBT51AECZEXJD2TZ/20201112/fr-par/s3/aws4_request -F x-amz-date=20201112T115301Z -F x-amz-signature=2eed2818b8fa1e833b12fab3b09c88987c6ba6be81786f9e94fac1c464b342f2 -F key=test.png -F file=@<FILE>
$

Release note for CHANGELOG:

Update generated mc config to have Signature Version v4

[remyleone]

@gmile Thanks a lot for your contribution :)