Allow to omit traits and environment API keys in `dumporganisationdatatolocalfs`

**Symptom:** `loaddata` raises `IntegrityError` when the target database already contains the same trait or API key.

**Root cause:** Both models define `natural_key()` (used during serialisation) but their managers lack `get_by_natural_key()` (needed during deserialisation). Without it, `loaddata` always attempts an INSERT rather than an UPDATE, hitting unique constraints.

**Fix:** To `dumporganisationdatatolocalfs` CLI management command, add an option to omit traits and environment keys entirely — these updates are not expected to be needed for the air-gapped env use case.