FIX: Fix reading in of caustom constants dictionary

sample-management-custom/caosdb-server/scripting/bin/export_sample_csv.py

@@ -355,6 +355,7 @@ EXTRACTORS = use_custom_names({
     "Longitude start": extract_lng_start,
     "Longitude stop": extract_lng_stop,
     "PDFReport": extract_pdf_id,
+    "PI": extract_person,
     "Sampling method": default_find,
     "Sphere": extract_sphere,
     "Start date": extract_start_date,

sample-management-custom/caosdb-server/scripting/bin/sample_helpers/utils.py

@@ -11,7 +11,12 @@ with open(os.path.join(Path(__file__).parent, "default_constants.yml")) as yaml_
 
 if os.path.isfile(os.path.join(Path(__file__).parent, "constants.yml")):
     with open(os.path.join(Path(__file__).parent, "constants.yml")) as custom_yaml_file:
-        CONSTANTS.update(yaml.safe_load(custom_yaml_file))
+        tmp_dict = yaml.safe_load(custom_yaml_file)
+        for key, value in tmp_dict.items():
+            if isinstance(value, dict):
+                CONSTANTS[key].update(value)
+            else:
+                CONSTANTS[key] = value
 
 
 def get_entity_name(name: str):