Add supplemental regex setting to validate username

CHANGES.rst

@@ -9,7 +9,12 @@ Changes
 `Unreleased <https://github.com/Ouranosinc/Magpie/tree/master>`_ (latest)
 ------------------------------------------------------------------------------------
 
-* Nothing new for the moment.
+Features / Changes
+~~~~~~~~~~~~~~~~~~
+
+* Create an additional settings/environment variable ``MAGPIE_SUPPLEMENTAL_USERNAME_REGEX`` that acts as an additional
+  check for whether a ``username`` is valid. This creates a further restriction on this value which is useful when there
+  are additional limits on the ``username`` that should be enforced by `Magpie`.
 
 .. _changes_3.36.0:
 

config/magpie.ini

@@ -61,6 +61,10 @@ magpie.user_registration_notify_enabled = false
 magpie.user_registration_notify_email_recipient =
 magpie.user_registration_notify_email_template =
 
+# --- user validation settings ---
+
+#magpie.supplemental_username_regex =
+
 # --- user assignment to groups with t&c ---
 magpie.group_terms_submission_email_template =
 magpie.group_terms_approved_email_template =

docs/configuration.rst

@@ -1428,6 +1428,28 @@ approval procedures.
         obtained from the :term:`Pending User`. Parameter ``approval_required`` is provided to generate alternative
         `Mako Template`_ contents in case different messages should be sent for each situation.
 
+.. _config_user_validation_settings
+
+User Validation Settings
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. envvar:: MAGPIE_SUPPLEMENTAL_USERNAME_REGEX
+
+    (Default: ``None``)
+
+    .. versionadded:: 3.36.1
+
+    A (python3 syntax) regular expression used to validate a ``username`` when creating or updating a `User`.
+
+    For example, if ``MAGPIE_SUPPLEMENTAL_USERNAME_REGEX='^\w+$'``, then a `User` can have ``userA`` as a ``username``
+    but not ``user.A`` or ``user-A``.
+
+    Note that `Magpie` enforces other restrictions that must also be met for a ``username`` to be considered valid.
+    This creates an additional restriction, it does not replace an existing restriction on the ``username``.
+
+    If this variable is empty or unset, then no additional ``username`` validations will be performed.
+
+
 .. envvar:: MAGPIE_USER_REGISTRATION_DECLINED_EMAIL_TEMPLATE
 
     (Default: |email_ur_declined_mako|_)

magpie/api/management/user/user_utils.py

@@ -872,6 +872,11 @@ def check_user_info(user_name=None, email=None, password=None, group_name=None,
         ax.verify_param(user_name, matches=True, param_name="user_name", param_compare=ax.PARAM_REGEX,
                         http_error=HTTPBadRequest,
                         msg_on_fail=s.Users_CheckInfo_UserNameValue_BadRequestResponseSchema.description)
+        supplemental_regex = get_constant("MAGPIE_SUPPLEMENTAL_USERNAME_REGEX", raise_missing=False)
+        if supplemental_regex:
+            ax.verify_param(user_name, matches=True, param_name="user_name", param_compare=supplemental_regex,
+                            http_error=HTTPBadRequest,
+                            msg_on_fail=s.Users_CheckInfo_UserNameValue_BadRequestResponseSchema.description)
         name_range = range(1, 1 + get_constant("MAGPIE_USER_NAME_MAX_LENGTH"))
         ax.verify_param(len(user_name), is_in=True, param_name="user_name", param_compare=name_range,
                         http_error=HTTPBadRequest,