Fix for multiple smartem grid registration

[d-j-hatton]

Currently multiple smartem grids are registered for each EPU atlas. Some of these are as a result of duplication in the code, some are because the Atlas.dm is edited triggering another endpoint hit. This should resolve all of these

[codecov]

Codecov Report

❌ Patch coverage is 75.86207% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.59%. Comparing base (8b02ba1) to head (e0fc681).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #887      +/-   ##
==========================================
- Coverage   55.10%   53.59%   -1.52%     
==========================================
  Files         102      103       +1     
  Lines       11367    12137     +770     
  Branches     1508     1683     +175     
==========================================
+ Hits         6264     6505     +241     
- Misses       4767     5264     +497     
- Partials      336      368      +32     

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