Feature: Remove spaces in group names that come from Entra

### Is there an existing request for this feature?

- [X] I have searched the existing issues and found none that matched mine

### Describe the feature

When using authd with Microsoft Entra ID, group names containing spaces are harder to work with in Linux terminals.
A good solution would be to automatically replace spaces (" ") with dashes ("-") in group names retrieved from Entra.

Example: My Group Name → my-group-name

Also to provide backwards compatibility, configuration option could be added in authd.yaml to enable or disable this transformation (e.g., transform_group_names = true).

### Describe the ideal solution

_No response_

### Alternatives and current workarounds

_No response_

### System information and logs

_No response_

### Relevant information

_No response_

### Double check your logs

- [X] I have redacted any sensitive information from the logs

Start by locating where authd retrieves group names from Microsoft Entra and how authd.yaml configuration is defined. Determine how the space-to-dash transformation should interact with existing names and verify that the configuration can enable or disable it without breaking backwards compatibility.

Written by the indexing model from the issue text.