Allow many_to_one() with arbitrary names

Without this change, the many side of the relationship is constrained
to have a certain name ("user") in this case. This change allows other
naming that is resolved via back_populates="field_name"

Author: adsharma

fquery/sqlmodel.py

@@ -59,8 +59,11 @@ def foreign_key(name):
     )
 
 
-def one_to_many():
-    return field(default=None, metadata={"SQL": {"relationship": True}})
+def one_to_many(back_populates=None):
+    return field(
+        default=None,
+        metadata={"SQL": {"relationship": True, "back_populates": back_populates}},
+    )
 
 
 def many_to_one(key_column=None, back_populates=None):

tests/test_sqlmodel.py

@@ -25,13 +25,21 @@ class User:
     updated_at: datetime = None
 
     friend: Optional["User"] = foreign_key("users.id")
-    reviews: List["Review"] = one_to_many()
+    reviews: List["Review"] = one_to_many("author")
+    visits: List["Visit"] = one_to_many()
 
 
 @sqlmodel
 class Review:
     id: int | None = None
     score: int
+    author: Optional[User] = many_to_one("users.id")
+
+
+@sqlmodel
+class Visit:
+    id: int | None = None
+    place: str
     user: Optional[User] = many_to_one("users.id")