Review `Authentication` scheme to see if we should move to using `Basic` authentication (introduced in `9.0+`)

[devraj]

Is your feature request related to a problem? Please describe.
The Gallagher CC documentation states that it accepts Basic authentication as of v9.0+

There are two ways you can pass the API key to the server: following an authorisation method of GGL-API-KEY, or (in 9.0 or later) in the style of HTTP Basic authentication: prefixed with a colon, Base64-encoded, and following an authorisation method of Basic.

as opposed the original custom header.

Should we move to using Basic authentication instead of the custom header?

Describe the solution you'd like
Investigate if using Basic authentication is preferable to the custom header and retrofit the authentication scheme in the utilities of the API client.

Note that exclusively moving to Basic authentication will render this library useless for older versions of the command centre.

It would be preferable to make Basic authentication the standard and the user of the library be able to pass a flag to use the custom header.

Describe alternatives you've considered
NA

Additional context
NA