[Notts Police] Allow staff to manage available states

[davea]

For FD-4703.
For https://github.com/mysociety/societyworks/issues/4608

[skip changelog]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.40%. Comparing base (f46c9a3) to head (f4ea046).
Report is 60 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5254      +/-   ##
==========================================
+ Coverage   82.39%   82.40%   +0.01%     
==========================================
  Files         409      409              
  Lines       32076    32085       +9     
  Branches     5119     5120       +1     
==========================================
+ Hits        26428    26439      +11     
+ Misses       4128     4126       -2     
  Partials     1520     1520              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.