feat(digitalocean): Add support for base64-encoded user-data

[zoispag]

Proposed Commit Message

feat(digitalocean): Add support for base64-encoded user-data

Updated DataSourceDigitalOcean to decode user_data using `util.maybe_b64decode()`. A unit test was added to verify the correct handling of base64-encoded user data.

Additional Context

Trying to use user-data provided by Terraform with base64_encode = true, I received the following error:

# /var/log/cloud-init-output.log
2025-06-24 13:37:13,389 - __init__.py[WARNING]: Unhandled non-multipart (text/x-not-multipart) userdata: 'b'Q29udGVudC1UeXBlOiBtdWx0'...'

This PR uses util.maybe_b64decode() similar to EC2 and Hetzner, to "potentially" decode base64-encoded user data.

Test Steps

Merge type

• [x] Squash merge using "Proposed Commit Message"
• [ ] Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

[dermotbradley]

As the DigitalOcean data source has been deprecated (#4194) since cloud-init 23.2, in preference to the ConfigDrive data source, is there any point in applying this change?

[github-actions[bot]]

Hello! Thank you for this proposed change to cloud-init. This pull request is now marked as stale as it has not seen any activity in 14 days. If no activity occurs within the next 7 days, this pull request will automatically close.

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