Add option to fix or freely choose random seeds

[1kastner]

This solves the first half of #9.

[codecov]

Codecov Report

Patch coverage: 97.89% and project coverage change: +0.04% 🎉

Comparison is base (a7d44f6) 94.56% compared to head (18eb43d) 94.60%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #191      +/-   ##
==========================================
+ Coverage   94.56%   94.60%   +0.04%     
==========================================
  Files         118      120       +2     
  Lines        4674     4730      +56     
==========================================
+ Hits         4420     4475      +55     
- Misses        254      255       +1     

Files Changed	Coverage Δ
.../database_connection/sqlite_database_connection.py	86.04% <83.33%> (+0.16%)	⬆️
...ation/repositories/random_seed_store_repository.py	97.72% <97.72%> (ø)
conflowgen/api/database_chooser.py	94.28% <100.00%> (+0.16%)	⬆️
conflowgen/application/models/random_seed_store.py	100.00% <100.00%> (ø)
...average_container_dwell_time_calculator_service.py	100.00% <100.00%> (ø)
conflowgen/database_connection/create_tables.py	100.00% <100.00%> (ø)
...owgen/domain_models/factories/container_factory.py	98.73% <100.00%> (-0.02%)	⬇️
...generator/abstract_truck_for_containers_manager.py	97.43% <100.00%> (+0.03%)	⬆️
...space_for_containers_delivered_by_truck_service.py	91.57% <100.00%> (+0.08%)	⬆️
...nerator/assign_destination_to_container_service.py	100.00% <100.00%> (ø)
... and 4 more

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