fix: prevent 'null' display when instructor family_name is missing

[rjv31]

Issue
Instructor profiles display "null" when family_name is missing.

2U Ticket
https://2u-internal.atlassian.net/browse/CATALOG-87

Root Cause
The marketing site integration was using full_name directly, which could include null values.

Fix
Updated name construction in MarketingSitePeople to safely handle missing family_name
Ensured only valid name parts are included
Added test coverage for missing and empty family_name cases
Testing
Verified profiles with and without family_name
Confirmed no "null" appears in marketing site payload

[ankit-sonata]

@rjv31 Looks good overall — focused fix and tests cover the missing/empty family_name cases well. Non-blocking thought: it may be worth adding a test for the case where both given_name and family_name are empty and only salutation exists, just to lock down expected behavior.

[rjv31]

Hi @ankit-sonata Thanks for the suggestion. I’ve updated the implementation and added coverage for the additional edge-case scenarios to align with the expected behavior when family_name is missing or empty while preserving salutation handling.