Add user service accounts

[cortadocodes]

Feature request

Use Case

Add the creation of user service accounts to the module.

Current state

We have maintainer service accounts for building and testing services. These have more permissions than needed for a user of a service.

Proposed Solution

• Add user_service_account_names input
• Assign them the minimum required permissions
• Create a user group and maintainer group and add service accounts to them
• Shift role assignment from service accounts to groups