Change default for service account creation to true

[samsternberg]

Problem

When running sky create-vault, the default for creating a service account is currently false. However, service accounts and API keys are essential for using the data operation commands (insert, deidentify, reidentify), so users typically need them.

Current Behavior

• Command line option: --create-service-account [boolean] defaults to false
• Interactive prompt: "Create a service account for this vault?" defaults to No

Solution

Change the default to true in both places to improve the out-of-box experience. Users can still opt out by:

• Using --create-service-account false on the command line
• Selecting "No" when prompted interactively

Expected Outcome

Service accounts are created by default, providing users with the API key needed for data operations without requiring an additional explicit step.