Add type coersion to SiriusPerson getters

[gregtyler]

Purpose

To ensure that the returned value matches the type specified in the method definition.

Fixes UML-3657 #patch

Approach

Used PHP's inline type casting

Learning

Check the logs first 😄 Though running locally was useful to ensure it would fix the underlying issue

Checklist

• I have performed a self-review of my own code
• I have added relevant logging with appropriate levels to my code
• New event_codes have been documented on the wiki page
• I have updated documentation (Confluence/GitHub wiki/tech debt doc) where relevant
• I have added tests to prove my work
• I have added welsh translation tags and updated translation files
• I have run an accessibility tool on any pages I have made changes to and fixed any issues found
• I have notified the Interaction Designer of any content changes so that appropriate screenshots/flow diagram changes can be made
• The product team have tested these changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.48%. Comparing base (f00760a) to head (2f240b2).
Report is 48 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2817      +/-   ##
============================================
+ Coverage     91.25%   91.48%   +0.23%     
- Complexity     1504     1587      +83     
============================================
  Files           309      345      +36     
  Lines          6393     6695     +302     
============================================
+ Hits           5834     6125     +291     
- Misses          542      553      +11     
  Partials         17       17              

Flag	Coverage Δ
use-an-lpa-admin	79.26% <ø> (ø)
use-an-lpa-api	97.47% <100.00%> (+0.10%)	⬆️
use-an-lpa-front	89.35% <ø> (-0.19%)	⬇️

Files with missing lines	Coverage Δ
...e-api/app/src/App/src/Service/Lpa/SiriusPerson.php	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes