* add role assumption for s3 source
* refactor role assumption to repeatable string
user can pass array of roles to assume
* refactor s3 chunks to handle passed roleARNs
* add role-session name
use timestamp to make dynamic
* add docstring for rolearn strings()
* make sure role ars are passed into source
* refactor role assumption functionality
break s3 bucket scanning into sep. function
* add log check on assume role
* fix role iteration
- Make sure s3 struct is populated with roles
- add separate new client instantiation for role-based access
- iterates through each role
* add comment
* protobuf revert for merge
* re-run make proto
* lint cleanup
* cleanup TODOs
* drop redundant switch case in assumerole client
* use less verbose 'ctx' designator
* breakout functionality from Chunks
- separate functions for:
- enumerating buckets to scan
- scanning objects within the buckets
* remake protobuf defs
* allow scan to continue on single bucket err
* add readme docs
* minor fixups