Add one-to-one relationship tutorial to docs

[fkromer]

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• I already read and followed all the tutorial in the docs and didn't find an answer.
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Example Code

n.a.

Description

It would be great to have an "how to" about one-to-one relationships directly in the official docs. An adaption of the sqlalchemy docs example about one-to-on relationships (https://docs.sqlalchemy.org/en/14/orm/basic_relationships.html#one-to-one) should do the job.

Operating System

Linux

Operating System Details

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SQLModel Version

n.a.

Python Version

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Additional Context

No response

[Beafowl-Pull]

you just need to make a simple relation like here: https://sqlmodel.tiangolo.com/tutorial/relationship-attributes/

[m0wer]

Not really. Since there's no option uselist=False for the relationship, you always get a list (so it's one-to-many) even if not possible (if you make the FK the PK).

[Kyu]

"workaround" for future readers: #132