fix(mtd): handle mtd with no contact principal retrieved

If not enough information could be retrieved to associate a metadata to an actor that is a "Contact Principal", then a specific user is used, and possibly created, to be associated as the "Contact principal" with the metadata.

This specific user has the following information:
- id_role, ID : 0 - particular positive integer value chosen to avoid conflict with other IDs, in particular those retrieved from the INPN
- desc_role, description : "Contact principal for 'orphan' metadata - i.e. with no 'Contact Principal' that could be retrieved during INPN MTD synchronisation"

In the case where not enough information could be retrieved to associate a metadata to an actor but the actor is not a "Contact principal", then the association is simply skipped and a warning message with details is logged.

backend/geonature/core/gn_meta/mtd/mtd_utils.py

@@ -6,6 +6,7 @@
 import uuid
 from flask import current_app
 
+from pypnusershub.routes import insert_or_update_role
 from sqlalchemy import select, exists
 from sqlalchemy.exc import SQLAlchemyError, IntegrityError
 from sqlalchemy.sql import func, update
@@ -237,6 +238,7 @@ def associate_actors(
     pk_value : str
         pk value: ID of the AF or DS
     """
+    type_mtd = "AF" if pk_name == "id_acquisition_framework" else "DS"
     for actor in actors:
         id_organism = None
         uuid_organism = actor["uuid_organism"]
@@ -293,7 +295,53 @@ def associate_actors(
             id_user_from_email = DB.session.scalar(
                 select(User.id_role).filter_by(email=email_actor).where(User.groupe.is_(False))
             )
-            values["id_role"] = id_user_from_email
+            if id_user_from_email:
+                values["id_role"] = id_user_from_email
+            else:
+                # If actor role is "Contact Principal", i.e. cd_nomenclature_actor_role = '1' ,
+                #   then we use a dedicated user for 'orphan' metadata - metadata with no associated "Contact principal" actor that could be retrieved 
+                #   the three non-null fields for `utilisateurs.t_roles` will be set to default:
+                #       - `groupe`: False - the role is a user and not a group
+                #       - `id_role`: generated by the nextval sequence
+                #       - `uuid_role`: generated by uuid_generate_v4()
+                #   in particular: 
+                #       - we do not specify field `email` even if `email_actor` is to be set
+                #       - only the field `dec_role` will be written to a non-default value, so as to identify this particular "Contact principal"-for-orphan-metadata user                
+                cd_nomenclature_actor_role_for_contact_principal = "1"
+                if cd_nomenclature_actor_role == cd_nomenclature_actor_role_for_contact_principal:
+                    # Retrieve the "Contact principal"-for-orphan-metadata user
+                    desc_role_for_user_contact_principal_for_orphan_metadata = "Contact principal for 'orphan' metadata - i.e. with no 'Contact Principal' that could be retrieved during INPN MTD synchronisation"
+                    id_user_contact_principal_for_orphan_metadata = 0
+                    user_contact_principal_for_orphan_metadata = DB.session.get(User, id_user_contact_principal_for_orphan_metadata)
+                    # /!\ Assert that the user with ID 0 retrieved is actually the "Contact principal"-for-orphan-metadata user with the right "desc_role"
+                    #   If an error is raised, one must choose how to handle this situation:
+                    #       - Check for the current user with ID 0
+                    #       - Possibly change the ID of this user to an ID other than 0
+                    #           /!\ Be careful to the other entries associated to this user
+                    #           /!\ Be careful when choosing a new ID : positive integer should be reserved for users retrieved from the INPN
+                    #       - Eventually change the code to: 
+                    #           - set an ID other than 0 for the "Contact principal"-for-orphan-metadata user
+                    #           - possibly allow to configure a different ID for different GN instances
+                    if user_contact_principal_for_orphan_metadata:
+                        assert user_contact_principal_for_orphan_metadata.desc_role == desc_role_for_user_contact_principal_for_orphan_metadata
+                    # If the user does not yet exist, create it
+                    else:
+                        dict_data_generated_user = {
+                            "id_role": id_user_contact_principal_for_orphan_metadata,
+                            "desc_role": user_contact_principal_for_orphan_metadata,
+                        }
+                        dict_data_generated_user = insert_or_update_role(
+                            data=dict_data_generated_user
+                        )
+                    # Commit to ensure that the insert from previous statement is actually committed
+                    DB.session.commit()
+                    values["id_role"] = id_user_contact_principal_for_orphan_metadata
+                else:
+                    logger.warning(
+                        f"MTD - actor association impossible for {type_mtd} with UUID '{uuid_mtd}' because no id_organism nor id_role could be retrieved - with the following actor information:\n"
+                        + format_str_dict_actor_for_logging(actor)
+                    )
+                    continue
         try:
             statement = (
                 pg_insert(CorActor)