Implement Endpoint for Retrieving Default Namespace in Portal UI Backend

[SergK]

Is your feature request related to a problem? Please describe.
There's a need to enhance the functionality and usability of our Portal UI by implementing a new backend endpoint for better namespace management.

Describe the solution you'd like
The implementation of a backend endpoint that primarily returns the default namespace value. This value can be determined through one of the following methods:

• Extracting it from the pod metadata.
• Defining it within the chart during the deployment process.
• If the above methods are not applicable, the namespace information can be skipped.

Describe alternatives you've considered
N/A

Additional context
Acceptance Criteria:

• The new endpoint is fully implemented and integrated into the Portal UI backend.
• The endpoint successfully returns the default namespace by extracting it from pod metadata or using the defined value in the chart during deployment.
• In cases where namespace information is unavailable or not applicable, the endpoint should handle this gracefully, adhering to predefined protocols.
• Thorough testing is conducted to validate the functionality, security, and performance of the endpoint.
• Documentation is updated to include details of the new endpoint, its usage, and any relevant configurations.