Avoid pointer redirection for Optional slices in Go

[hculea]

In Go, optional values are represented by pointers. This makes sense for most types. For example, using a "*bool" pointer allows for the type to express three values: nil, true or false.

In the 1Password SDKs, we expose the types generated by typeshare (e.g. see the types for Go) to be user facing.

Typeshare currently uses a pointer redirection to mark the Go types as optional. While most of the values are translated correctly, using a pointer to a slice (i.e. the translation of Vec<T> currently is []*string) is not usual in Go, and it leads to more complex code for the users of the SDK.

This is because, in Go, slices are already reference types. That is, passing a slice around passes a reference to the underlying data.

However, an edge case can occur:

type A struct {
    Slice []string `json:",omitempty"`
}

type B struct {
    Slice *[]string `json:",omitempty"`
}

For type A, both Slice: nil and Slice: []string{} have the same JSON serialisation (Slice is omitted).

For type B Slice: nil and Slice: []string{} both have a different JSON serialisation. In the first case, Slice is omitted. In the second case the field has the value [].

This, however, is rarely applicable in practice, and having this feature does not justify exposing an unintuitive user interface. Therefore, this PR is adding a configuration option disabling that for Go.

[seanaye]

Could we add a unit test to assert this setting works as expected in both cases

[seanaye]

The description of the problem in the PR description was very good. Could we copy/paste some of that prose here as a doc comment