Add foreign keys to rdkit tables

[skearnes]

Add foreign keys to rdkit tables so that they can be joined directly instead of having to go through SMILES.

[codecov]

Codecov Report

Merging #702 (5570357) into main (4961279) will increase coverage by 0.27%.
Report is 5 commits behind head on main.
The diff coverage is 86.95%.

@@            Coverage Diff             @@
##             main     #702      +/-   ##
==========================================
+ Coverage   69.33%   69.60%   +0.27%     
==========================================
  Files          23       23              
  Lines        2322     2356      +34     
  Branches      589      594       +5     
==========================================
+ Hits         1610     1640      +30     
- Misses        598      601       +3     
- Partials      114      115       +1     

Files Changed	Coverage Δ
ord_schema/orm/scripts/add_datasets.py	47.16% <25.00%> (-1.85%)	⬇️
ord_schema/orm/conftest.py	96.29% <90.00%> (+0.46%)	⬆️
ord_schema/orm/database.py	92.78% <91.66%> (-0.46%)	⬇️
ord_schema/orm/mappers.py	96.96% <100.00%> (+0.07%)	⬆️
ord_schema/orm/rdkit_mappers.py	91.46% <100.00%> (ø)
ord_schema/templating.py	95.31% <100.00%> (+0.15%)	⬆️