custom_profile_field changes and testing

[LearningCChang]

Custom_profile_field changes: check whether name and hint inputs are valid; they will be updated if the name and hint fields are not empty, otherwise, they will remain the same.

Test functions:

1. Test adding a field with valid name and hint. (Ensures that the function correctly handles valid inputs and that the notification function is triggered)
2. Test adding a field with an empty name. (Verifies that the function can handle an empty string for the name parameter and that the field is created with an empty name)
3. Test the behavior when both name and hint are None. (Checks if the function defaults to an empty string for name and None for hint correctly)
4. Test the addition of a field with required=None (This tests the required parameter defaults to False if None is passed)
5. Test adding a field with display_in_profile_summary=False (Verifies that the field is created correctly without displaying in the profile summary)