feat: Make USERNAME_MIN_LENGTH customizable

Author: stoorx

openedx/core/djangoapps/user_api/accounts/__init__.py

@@ -14,7 +14,7 @@
 NAME_MAX_LENGTH = 255
 
 # The minimum and maximum length for the username account field
-USERNAME_MIN_LENGTH = 2
+USERNAME_MIN_LENGTH = getattr(settings, 'USERNAME_MIN_LENGTH', 2)
 # Note: 30 chars is the default for historical reasons. Django uses 150 as the username length since 1.10
 USERNAME_MAX_LENGTH = getattr(settings, 'USERNAME_MAX_LENGTH', 30)