Generate DeepCopy methods

[spolti]

What would you like to be added:
When working with hard typed Workflow definition, we might need to define the base workflow struct and import the types from sdk-go.

import github.com/serverlessworkflow/sdk-go/v2
...
type WorkflowSpec struct {
	Retry      model.Retry      `json:"retry"`
}

Such scenario can thrown the following compilation error:

api/v08/zz_generated.deepcopy.go:807:13: in.Retries.DeepCopyInto undefined (type model.Retry has no field or method DeepCopyInto)

We can rely on https://pkg.go.dev/k8s.io/gengo/examples/deepcopy-gen
to have these automatically generated.

[amadhusu]

/assign

[spolti]

@amadhusu there is a draft here, if you want to continue from there
https://github.com/spolti/sdk-go/tree/deepCopy