Use app identity for deployment of storage accounts

[Ceredron]

Description

We change deployment of app to use subscription scope so that we can use RBAC to give container app access to deploying storage accounts instead of using a separate service principal for it.

This way we avoid using any more secrets than necessary.

Related Issue(s)

• #{issue number}

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)
• All tests run green

Documentation

• User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)