📝 Update instructions about how to make a foreign key required in docs/tutorial/relationship-attributes/define-relationships-attributes.md

[jalvaradosegura]

Hi 👋

I wanted to make a foreign key mandatory and I think that this part of the tutorial was talking about that. I followed those steps but the foreign key wasn't mandatory yet. It didn't show the red "*" on the Swagger interface and my unit tests were passing without it.

I completely removed the the default parameter of the Field object, of the foreign key, and after that, I got the red "*" and my unit tests started to fail.

I'm not sure if this is how it is supposed to be done, but in case it is, here is the PR :)

Just in case, here I'm sharing a little code with an app to test this. First run it as it is (the current state of the code is after applying the instructions of the docs before this PR) and then go to the /docs and check the schema for the heroes endpoint. team_id shouldn't be mandatory. But if you remove the default parameter of the Field object of the team_id attribute, it should become mandatory

from typing import List, Optional

from fastapi import FastAPI
from sqlmodel import Field, Relationship, Session, SQLModel, create_engine


class Team(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    headquarters: str

    heroes: List["Hero"] = Relationship(back_populates="team")


class Hero(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str = Field(index=True)
    secret_name: str
    age: Optional[int] = Field(default=None, index=True)

    team_id: int = Field(default=None, foreign_key="team.id")
    team: Team = Relationship(back_populates="heroes")


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

engine = create_engine(sqlite_url, echo=True)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/")
def create_hero(hero: Hero):
    with Session(engine) as session:
        session.add(hero)
        session.commit()
        session.refresh(hero)
        return hero

ps: I'm having tons of fun with your libraries! thanks

[github-actions]

📝 Docs preview for commit b3386f3 at: https://635230ff381fa0723e828238--sqlmodel.netlify.app

[codecov]

Codecov Report

Base: 98.49% // Head: 98.49% // No change to project coverage 👍

Coverage data is based on head (b3386f3) compared to base (ea79c47).
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Additional details and impacted files

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  Coverage   98.49%   98.49%           
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  Files         185      185           
  Lines        5856     5856           
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  Hits         5768     5768           
  Misses         88       88           

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[github-actions]

📝 Docs preview for commit 8b6a4d6 at: https://639ce0735cc7fa00ac620965--sqlmodel.netlify.app

[tiangolo]

Great, thanks! 🍰