Unify all authTokens, auth functions and API calls

[NowinskiK]

Currently, public functions call one of these functions to ensure the connection is established and is valid (token not expired):

• Test-TokenExpired (only)
• Confirm-FabricAuthToken

This is because code comes from three/four different projects, and we are going to standardise it later.
The goal is to select only one and unify all functions using only one selected function.
Example of current situation:

This will also be an opportunity to remove duplicated code like this and wrap it up into Test-TokenExpired:

        Write-Message -Message "Validating token..." -Level Debug
        Test-TokenExpired
        Write-Message -Message "Token validation completed." -Level Debug