fix: persist terrain temporal identity

backend/tests/test_spw_terrain_service.py

@@ -164,8 +164,18 @@ def test_spw_terrain_acquisition_persists_bounded_dng_raster_and_provenance(
     assert captured["source_metadata"]["coverage_zones"] == ["wallonia"]
     assert captured["provenance_metadata"]["resampling"] == "bilinear"
     assert captured["provenance_metadata"]["source_sha256"] == source_digest
+    assert captured["temporal_series_key"].startswith("spw:terrain:mnt:")
     assert captured["temporal_granularity"] == "period"
     assert captured["valid_from"].date().isoformat() == "2021-02-19"
+    temporal = DatasetService._validate_temporal_metadata(
+        temporal_series_key=captured["temporal_series_key"],
+        observed_at=captured["observed_at"],
+        valid_from=captured["valid_from"],
+        valid_to=captured["valid_to"],
+        temporal_granularity=captured["temporal_granularity"],
+        source_version=captured["source_version"],
+    )
+    assert temporal["temporal_granularity"] == "period"
     with rasterio.MemoryFile(captured["content"]) as memory:
         with memory.open() as derived:
             assert derived.crs.to_epsg() == 3812