Management of existing Spacelift resources

[eliecharra]

Today we cannot manage a resource that already exists in Spacelift through the operator.
If you try to create a Context with the same name as a context that already exists, the operator will complain because of a name collision.

We could introduce a way to create resources by both id and name.
If id is set this means that you want to manage a resource that already exists, and thus allow us to manage an existing Spacelift resource with the operator.
This could mimic the OpenTofu import behavior.