Switch Key vault from Access Policies to RBAC

[gopher194]

Switch from Access Policy to RBAC Access control to Key vault

This issue is for a:

- [ ] bug report -> please search issues before submitting
- [x] feature request
- [ ] documentation issue or request
- [ ] regression

Notes

• Test manually in DEV environment
• Check the API App service managed identity access to get the DB Connection string
• Change API App settings to get the Connection string from an App Settings pulled from key vault. Format is: "@Microsoft.KeyVault(VaultName=kv-devexdays-app-dev-01;SecretName=AZURE-SQL-CONNECTION-STRING)"
• Update the bicep code to:
  • switch to managed identity + role assignment for the API App Service access
  • remove access policies
• Give Team2 users RBAC role to access the Key vault secrets