Add documentation to client.go and instance.go public methods

[naikmubashir]

📚 Documentation Enhancement

Addresses issue #279 by adding comprehensive Go documentation to all public methods in client.go and instance.go.

Key Changes:

• Fixed UpdateInstanceBandwidth documentation (was incorrect)
• Added documentation to 9 methods in client.go
• Added documentation to 25 methods in instance.go

Standards Applied:

• Clear purpose descriptions
• Parameter and return value documentation
• Error condition explanations
• Usage warnings for destructive operations

All documentation follows Go conventions and significantly improves API usability.

Closes #279

[giornetta]

Hi @naikmubashir thank you for this and sorry for the delay!

I'll look into this as soon as I have a minute!

[giornetta]

I don't think this documentation style is great: it's very verbose and the parameters/returns descriptions are often unnecessary, and their names and types should be self documenting in my opinion.

There are cases where a more detailed description for parameters might be necessary, for example to explain func NewClientForTesting(responses map[string]string) (*Client, *httptest.Server, error), so I would keep the details only in these cases