allow user role to create/list/delete buckets (but bucket policy still affects)

[guymguym]

Explain the changes

1. Accounts with "user" role were rejected by the rpc auth from performing bucket operations - create, update, delete, list.
2. Changed to allow it by the rpc.
3. Still, the specific bucket policy and account options will only let users that are allowed per a bucket and account.
4. For example create_bucket permission is based on account.allow_bucket_creation which can be specified in create_account api.

Issues: Fixed #xxx / Gap #xxx

1. NA

Testing Instructions:

1. Create an account with "user" role and use the account access/secret keys to perform bucket operations:

npm run api -- account create_account '{ "name":"alice", "email":"alice@noobaa.io", "has_login":false, "s3_access":true, "allow_bucket_creation":true, "roles":["user"], "default_resource":"backingstores" }' --json

export AWS_ACCESS_KEY_ID=$(npm run api -- account read_account '{"email":"alice@noobaa.io"}' --json | tail -1 | jq -r '.access_keys[0].access_key')
export AWS_SECRET_ACCESS_KEY=$(npm run api -- account read_account '{"email":"alice@noobaa.io"}' --json | tail -1 | jq -r '.access_keys[0].secret_key')

❯ aws s3 --endpoint http://localhost:6001 mb s3://alice-bucket1
make_bucket: alice-bucket1
❯ aws s3 --endpoint http://localhost:6001 ls
2023-06-12 10:33:41 alice-bucket1
❯ aws s3 --endpoint http://localhost:6001 ls s3://alice-bucket1
❯ aws s3 --endpoint http://localhost:6001 rb s3://alice-bucket1
remove_bucket: alice-bucket1

• Doc added/updated
• Tests added