Defer default otel_resource creation in SolarWindsApmConfig.__init__

[Copilot]

This PR addresses the single review comment on PR #807: avoid evaluating Resource.create() in the constructor signature and apply the requested initialization pattern directly. The change is scoped to that comment only.

• Default argument behavior

  • Replaced eager default construction in SolarWindsApmConfig.__init__:
    • from otel_resource: Resource = Resource.create()
    • to otel_resource: Optional[Resource] = None

• Runtime initialization

  • Added in-method fallback to preserve behavior for callers that omit otel_resource:
    • if otel_resource is None: otel_resource = Resource.create()

• Typing/docstring alignment

  • Updated parameter typing and docstring to reflect None-default semantics while keeping backward-compatible behavior.

def __init__(self, otel_resource: Optional[Resource] = None, **kwargs: int) -> None:
    if otel_resource is None:
        otel_resource = Resource.create()
    ...