Problems with Strings as primary_key/foreign_key on SQL Dialects that require Length

[Freshpinguin]

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Example Code

from sqlmodel import SQLModel, Field, create_engine, Relationship, Column, String
from typing import Optional, List

engine = create_engine(
    "mariadb+mariadbconnector://..."
)

class User(SQLModel, table=True):

    name: str = Field(sa_column=Column(String(3), primary_key=True))

    sessions: List["UserSession"] = Relationship(back_populates="user")

class UserSession(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)

    # user_name: str = Field(foreign_key="user.name")
    # raises: sqlalchemy.exc.CompileError: (in table 'usersession', column 'user_name'): VARCHAR requires a length on dialect mariadb

    user_name: str = Field(sa_column=Column(String(3), foreign_key=True))
    # Doenst work as sqlalchemies Column does not a have a key word argument for foreign_key.

    user: User = Relationship(back_populates="sessions")

SQLModel.metadata.create_all(engine)

Description

Iam trying to have a string as a primary key and foreign Key in SQLModel using MariaDB.
As the MariaDB dialect requires me to define the length of a string, i need to define fields using the sa_column key word argument in Field using the Column Object from SQLAlchemy.
This works for primary_key as the SQLAlchemy Object Column supports the key word argument primary_key.
But it doesn't support foreign_key so that does not work.
Also passing sa_column and foreign_key or primary_key to Field raises:
RuntimeError(
"Passing primary_key is not supported when "
"also passing a sa_column"
)
from SQLModels FieldInfo Object.

Operating System

Windows

Operating System Details

No response

SQLModel Version

0.0.16

Python Version

Python 3.12.0

Additional Context

This is my first time ever asking a question on Github, so feedback is appreciated.