refactor: switch from awsutil to awsutilv2 (#34)

* fix(storage): Storage Assume Role Support

This commit introduces fixes to enable operators to use AWS dynamic
credentials on the storage side of this plugin, namely validation,
improved credential lifecycle management to allow for storage buckets to
be updated from static to dynamic credentials and vice versa, and a new
way to determine credential types.

It also introduces new tests for dynamic credential usage for the
various functions.

* fix(storage): Static rotated creds being deleted on plugin err

On Storage Bucket update, when we determine if the credentials are to be
updated to new ones, we call `credState.ReplaceCreds`.

This call, if the old credentials were managed by us (rotated at create
time), will delete the old credentials and set the new ones onto
credState.

We called this function without validating if the incoming credentials
are valid. This could get the bucket in a state where where, while we'd
return an update error if the incoming credentials weren't working with
S3 (err in the dry run process that happens at the end of the update),
we'd also silently delete the old credentials the bucket used, rendering
the bucket completely broken.

---------

Co-authored-by: Hugo <hugoamvieira@users.noreply.github.com>

README.md

@@ -17,7 +17,7 @@ and then the given credential will be revoked. In this way, after rotation,
 only Boundary knows the client secret in use by this plugin. More information
 about AWS static credentials can be found [here](https://docs.aws.amazon.com/sdkref/latest/guide/feature-static-credentials.html).
 
-Credential rotation can be turned off by setting the 
+Credential rotation can be turned off by setting the
 `disable_credential_rotation` attribute to `true`.
 
 ### Assume Role Credentials
@@ -48,7 +48,7 @@ The plugin fetches hosts through the
 [DescribeInstances](https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeInstances.html)
 call.
 
-[Getting Started](https://github.com/hashicorp/boundary-plugin-aws/plugin/service/host/README.md)
+[Getting Started](plugin/service/host/README.md)
 
 ## Storage Bucket
 
@@ -60,7 +60,7 @@ these storage bucket resources can in turn be associated to targets within
 Boundary.
 
 At creation, update or deletion of a storage bucket of this type, configuration of the
-plugin is performed via the attribute/secret values passed to the create, update, or 
+plugin is performed via the attribute/secret values passed to the create, update, or
 delete calls actions. The values passed in to the plugin here are the attributes set
 on on a storage bucket in boundary.
 
@@ -76,4 +76,4 @@ The plugin fetches metadata about the files through the
 [HeadObject](https://docs.aws.amazon.com/AmazonS3/latest/API/API_HeadObject.html)
 call.
 
-[Getting Started](https://github.com/hashicorp/boundary-plugin-aws/plugin/service/storage/README.md)
+[Getting Started](plugin/service/storage/README.md)