[FEATURE]: Support adding policies to the buckets

[shanduur]

Are you interested in contributing to the development of this feature?

Yes

Is your feature request related to a problem? Please describe.

Currently, our driver does not support the dynamic application of policies during the creation of buckets. This limits the flexibility and control over bucket configurations, making it necessary to apply policies manually after the bucket creation process. Automating this step would streamline the workflow and reduce the risk of misconfigurations or omissions.

Describe the solution you'd like.

Add a common parameter that can be included in the BucketClass specification to dynamically create desired policies. This can be specified using a new parameter, cosi.linode.com/v1/policy, which will accept a JSON formatted policy, e.g.:

parameters:
  cosi.linode.com/v1/policy: |
    {
      "Version": "2012-10-17",
      "Statement": [
        {
          "Effect": "Allow",
          "Principal": "*",
          "Action": "s3:GetObject",
          "Resource": "arn:aws:s3:::{{ .BucketName }}/*"
        }
      ]
    }

This should also support templating - e.g. by referencing the .BucketName field.

flowchart TD
    policyField[cosi.linode.com/v1/policy] -->|read| policyTemplate(Policy Template)
    policyTemplate -->|execute text/template| policy(Policy)
    policy -->|validate| validatedPolicy[Validated Policy]
    validatedPolicy -->|apply| appliedPolicy[Applied Policy]

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Describe alternatives you've considered.

N/A

Additional Information

The implementation should ensure that:

1. Policies are validated to ensure they are in correct JSON format.
2. The system handles scenarios where the policy application might fail, providing appropriate error messages and possibly rollback mechanisms.
3. The existing functionality remains unaffected if no policy is specified.

This enhancement will improve the ease of use and flexibility of our bucket management system, allowing for more robust and automated configurations.

Suggested libraries:

• https://github.com/minio/minio-go (small in size)
• https://github.com/aws/aws-sdk-go-v2 (reference implementation, might bloat the executable a little)