support copy_object copy source string input

[eden-ohana]

Currently supports only dictionary.

CopySource='string' or {'Bucket': 'string', 'Key': 'string', 'VersionId': 'string'}

Reference

Not trivial because If you want to provide the copy source for an S3 access point as a string instead of a dictionary, the ARN provided must be the full S3 access point object ARN (i.e. {accesspoint_arn}/object/{key})