Add yank_message field to API version responses

[Turbo87]

This field can currently only be set directly in the database, but introducing it in a dedicated commit/PR makes the diff of the commit/PR that introduces the update API much more manageable. This PR was extracted from the PR linked below :)

/cc @Rustin170506

Related:

• Support yank a package with a message #9193
• Add PATCH /crates/:crate/:version route #9423

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.07%. Comparing base (ffa4d86) to head (0ca0c86).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9437   +/-   ##
=======================================
  Coverage   89.06%   89.07%           
=======================================
  Files         285      285           
  Lines       28938    28941    +3     
=======================================
+ Hits        25774    25778    +4     
+ Misses       3164     3163    -1     

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