Add config option exit_after_insert to exit API after inserting data

[ml-evs]

This allows for the standardized ingestion procedure to occur in parallel to a running API, with zero downtime.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.54%. Comparing base (19ab866) to head (049a914).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
optimade/server/main.py	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2223      +/-   ##
==========================================
- Coverage   90.59%   90.54%   -0.06%     
==========================================
  Files          75       75              
  Lines        4860     4865       +5     
==========================================
+ Hits         4403     4405       +2     
- Misses        457      460       +3     

Flag	Coverage Δ
project	90.54% <50.00%> (-0.06%)	⬇️
validator	90.54% <50.00%> (-0.06%)	⬇️

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