modify slug_generator to include .

[DininduSenanayake]

Previous implementation will not preserve dots in usernames. For example, "john.doe" would be converted to "john-doe".

To modify the function to accept usernames with dots, we need to update the NON_ALPHANUM_PATTERN and possibly adjust the OBJECT_PATTERN.

key changes made:

1. Added dot (".") to LOWER_PLUS_HYPHEN array.
2. Updated OBJECT_PATTERN and LABEL_PATTERN to include dot.
3. Modified NON_ALPHANUM_PATTERN to allow dots: /[^a-z0-9\.]+/

didn't need to modify the extract_safe_name method itself because the changes to NON_ALPHANUM_PATTERN are sufficient to preserve dots. ( I think)

[DininduSenanayake]

Updated test-suite for

• Dots are preserved in valid usernames.
• Multiple dots are handled correctly.
• Leading and trailing dots are removed.
• Mixtures of dots and hyphens are preserved.
• Long names with dots are truncated and hashed appropriately.
• Slugs don't end with hyphens or dots