Add destroy on merge workflow

[gillettmoj]

Purpose

Briefly describe the purpose of the change, and/or link to the JIRA ticket for context

Fixes UML-####

Approach

Explain how your code addresses the purpose of the change

Learning

Any tips and tricks, blog posts or tools which helped you. Plus anything notable you've discovered about the Use a Lasting Power of Attorney service

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 91.28%. Comparing base (f00760a) to head (f4be019).
Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2757      +/-   ##
============================================
+ Coverage     91.25%   91.28%   +0.03%     
- Complexity     1504     1512       +8     
============================================
  Files           309      310       +1     
  Lines          6393     6416      +23     
============================================
+ Hits           5834     5857      +23     
  Misses          542      542              
  Partials         17       17              

Flag	Coverage Δ
use-an-lpa-admin	79.26% <ø> (ø)
use-an-lpa-api	97.39% <ø> (+0.02%)	⬆️
use-an-lpa-front	89.54% <ø> (ø)