Use real Collection 4 manifest and correct data object IDs

Address review feedback:
- Verified the new water data object IDs against the real Collection 4
  (v4.01) product that caused the original failure (fetched from the
  Planetary Computer sentinel3euwest store). The actual IDs are
  chlor_aData and fluoData (not the previously guessed chlorAData /
  fluorescenceData); iopLsdData was correct.
- Move the water band lookup from a function-scoped dict to the
  module-level OLCI_L2_WATER_BAND_KEYS constant.
- Replace the synthetic regex-based tests with tests that use a real
  Collection 4 manifest committed under tests/data-files (NetCDF assets
  stripped to header-only stubs, matching the existing fixtures), plus a
  command-level test that builds and validates a full item.

Author: Derek Tan

src/stactools/sentinel3/constants.py

@@ -737,11 +737,58 @@
 # products were added. See:
 # https://user.eumetsat.int/news-events/news/update-to-sentinel-3-olci-level-2-water-processing
 OLCI_L2_WATER_ASSET_KEYS_C4 = [
-    "chlorAData",
-    "fluorescenceData",
+    "chlor_aData",
+    "fluoData",
     "iopLsdData",
 ]
 
+# Maps each OLCI L2 water data object ID to the OLCI bands it is derived from.
+# Data objects without an entry here (annotation files, and the Collection 4
+# chlor_a/fluorescence/iop_lsd products) carry no eo:bands.
+OLCI_L2_WATER_BAND_KEYS = {
+    "chlNnData": [
+        "Oa01",
+        "Oa02",
+        "Oa03",
+        "Oa04",
+        "Oa05",
+        "Oa06",
+        "Oa07",
+        "Oa08",
+        "Oa09",
+        "Oa10",
+        "Oa11",
+        "Oa12",
+        "Oa16",
+        "Oa17",
+        "Oa18",
+        "Oa21",
+    ],
+    "tsmNnData": [
+        "Oa01",
+        "Oa02",
+        "Oa03",
+        "Oa04",
+        "Oa05",
+        "Oa06",
+        "Oa07",
+        "Oa08",
+        "Oa09",
+        "Oa10",
+        "Oa11",
+        "Oa12",
+        "Oa16",
+        "Oa17",
+        "Oa18",
+        "Oa21",
+    ],
+    "chlOc4meData": ["Oa03", "Oa04", "Oa05", "Oa06"],
+    "iopNnData": ["Oa01", "Oa12", "Oa16", "Oa17", "Oa21"],
+    "iwvData": ["Oa18", "Oa19"],
+    "trspData": ["Oa04", "Oa06"],
+    "wAerData": ["Oa05", "Oa06", "Oa17"],
+}
+
 SLSTR_L1_ASSET_KEYS = [
     "SLSTR_S1_RAD_AN_Data",
     "SLSTR_S2_RAD_AN_Data",

src/stactools/sentinel3/metadata_links.py

@@ -559,53 +559,6 @@ def strip_prefix(prefix: str, content: str) -> str:
                     asset_identifier_list.append(asset_key)
                     asset_list.append(asset_obj)
             elif "_WFR_" in product_type:
-                # Map each water data object ID to the OLCI bands it is
-                # derived from. Data objects without an entry here (annotation
-                # files, and the Collection 4 chlor_a/fluorescence/iop_lsd
-                # products) carry no eo:bands.
-                band_key_map = {
-                    "chlNnData": [
-                        "Oa01",
-                        "Oa02",
-                        "Oa03",
-                        "Oa04",
-                        "Oa05",
-                        "Oa06",
-                        "Oa07",
-                        "Oa08",
-                        "Oa09",
-                        "Oa10",
-                        "Oa11",
-                        "Oa12",
-                        "Oa16",
-                        "Oa17",
-                        "Oa18",
-                        "Oa21",
-                    ],
-                    "tsmNnData": [
-                        "Oa01",
-                        "Oa02",
-                        "Oa03",
-                        "Oa04",
-                        "Oa05",
-                        "Oa06",
-                        "Oa07",
-                        "Oa08",
-                        "Oa09",
-                        "Oa10",
-                        "Oa11",
-                        "Oa12",
-                        "Oa16",
-                        "Oa17",
-                        "Oa18",
-                        "Oa21",
-                    ],
-                    "chlOc4meData": ["Oa03", "Oa04", "Oa05", "Oa06"],
-                    "iopNnData": ["Oa01", "Oa12", "Oa16", "Oa17", "Oa21"],
-                    "iwvData": ["Oa18", "Oa19"],
-                    "trspData": ["Oa04", "Oa06"],
-                    "wAerData": ["Oa05", "Oa06", "Oa17"],
-                }
                 # Iterate over both the legacy water keys and the Collection 4
                 # (v4.01) additions. Data objects that are not present in this
                 # particular manifest are skipped, so the same code handles
@@ -617,8 +570,8 @@ def strip_prefix(prefix: str, content: str) -> str:
                 ):
                     if len(manifest.findall(f".//dataObject[@ID='{asset_key}']")) == 0:
                         continue
-                    if asset_key in band_key_map:
-                        band_key_list = band_key_map[asset_key]
+                    if asset_key in constants.OLCI_L2_WATER_BAND_KEYS:
+                        band_key_list = constants.OLCI_L2_WATER_BAND_KEYS[asset_key]
                     elif asset_key.startswith("Oa") and asset_key.endswith(
                         "_reflectanceData"
                     ):