Added soft deletes to all deletion functions and added deleted_at filters as required

gatehouse_app/services/external_auth/linking.py

@@ -219,10 +219,11 @@ def authenticate_with_provider(
     auth_method = AuthenticationMethod.query.filter_by(
         method_type=provider_type,
         provider_user_id=user_info["provider_user_id"],
+        deleted_at=None,
     ).first()
 
     if not auth_method:
-        existing_user = User.query.filter_by(email=user_info["email"]).first()
+        existing_user = User.query.filter_by(email=user_info["email"], deleted_at=None).first()
 
         if existing_user:
             AuditService.log_external_auth_login_failed(
@@ -286,12 +287,13 @@ def unlink_provider(
     auth_method = AuthenticationMethod.query.filter_by(
         user_id=user_id,
         method_type=provider_type,
+        deleted_at=None,
     ).first()
 
     if not auth_method:
         raise ExternalAuthError("Provider not linked", "PROVIDER_NOT_LINKED", 400)
 
-    other_methods = AuthenticationMethod.query.filter_by(user_id=user_id).count()
+    other_methods = AuthenticationMethod.query.filter_by(user_id=user_id, deleted_at=None).count()
     if other_methods <= 1:
         raise ExternalAuthError(
             "Cannot unlink the last authentication method",