Fix deployment env vars not working if is_secret=True

[vandyliu]

Description

• Previously, environment variables with is_secret=True emit errors in Terraform
• On create, update, and read for deployment resources, we must give Terraform the actual secret value so it doesnt error out and see inconsistencies. The value field is sensitive though so it is not outputted, however it is necessary so Terraform doesn't complain and error out.

🎟 Issue(s)

#45

🧪 Functional Testing

• Added acceptance integration tests
• Also works with imported deployment

📸 Screenshots

📋 Checklist

• Rebased from the main (or release if patching) branch (before testing)
• Added/updated applicable tests
• Added/updated examples in the examples/ directory
• Tested against Astro-API
• Communicated to/tagged owners of respective clients potentially impacted by these changes.
• Updated any related documentation