🚨(pylint) make pylint work and fix issues found

Pylint was not installed and wrongly configured. After making
it work, we fix all the issues found so it can be added to our
CI requirements.

src/backend/core/models.py

@@ -4,30 +4,23 @@ Declare and configure the models for the People core application
 import json
 import os
 import uuid
-from datetime import timedelta
-from zoneinfo import ZoneInfo
 
 from django.conf import settings
 from django.contrib.auth import models as auth_models
 from django.contrib.auth.base_user import AbstractBaseUser
-from django.contrib.postgres.fields import ArrayField
-from django.contrib.postgres.indexes import GinIndex
 from django.core import exceptions, mail, validators
 from django.db import models
-from django.db.models import F, Q
-from django.utils import timezone as timezone_util
 from django.utils.functional import lazy
-from django.utils.text import capfirst, slugify
 from django.utils.translation import gettext_lazy as _
 
 import jsonschema
-from dateutil.relativedelta import relativedelta
+from rest_framework_simplejwt.exceptions import InvalidToken
 from rest_framework_simplejwt.settings import api_settings
 from timezone_field import TimeZoneField
 
 current_dir = os.path.dirname(os.path.abspath(__file__))
 contact_schema_path = os.path.join(current_dir, "jsonschema", "contact_data.json")
-with open(contact_schema_path, "r") as contact_schema_file:
+with open(contact_schema_path, "r", encoding="utf-8") as contact_schema_file:
     contact_schema = json.load(contact_schema_file)
 
 
@@ -43,7 +36,7 @@ class BaseModel(models.Model):
     """
     Serves as an abstract base model for other models, ensuring that records are validated
     before saving as Django doesn't do it by default.
-    
+
     Includes fields common to all models: a UUID primary key and creation/update timestamps.
     """
 
@@ -140,7 +133,7 @@ class Contact(BaseModel):
         # Check if the contact points to a base contact that itself points to another base contact
         if self.base_id and self.base.base_id:
             raise exceptions.ValidationError(
-                "A contact cannot point to a base contact that itself points to another base contact."
+                "A contact cannot point to a base contact that itself points to a base contact."
             )
 
         # Validate the content of the "data" field against our jsonschema definition
@@ -159,6 +152,7 @@ class UserManager(auth_models.UserManager):
     """
 
     def get_queryset(self):
+        """Always select the related contact when doing a query on users."""
         return super().get_queryset().select_related("profile_contact")
 
 
@@ -467,8 +461,8 @@ def oidc_user_getter(validated_token):
             **{api_settings.USER_ID_FIELD: user_id}, profile_contact=contact
         )
 
-    # If the identity in the token is seen for the first time, make it the main email. Otherwise, update the
-    # email and respect the main identity set by the user
+    # If the identity in the token is seen for the first time, make it the main email.
+    # Otherwise, update the email and respect the main identity set by the user
     if email := validated_token["email"]:
         Identity.objects.update_or_create(
             user=user, email=email, create_defaults={"is_main": True}