Fix login errors, add get /users and get /user (username or id) routes.

app/models/user.py

@@ -1,7 +1,7 @@
 from sqlmodel import Field, SQLModel
 
 
-class User(SQLModel, table=True):
+class User(SQLModel):
     id: int | None = Field(default=None, primary_key=True)
 
     username: str
@@ -13,5 +13,5 @@ class UserIn(User):
     password: str
 
 
-class UserInDB(User):
+class UserInDB(User, table=True):
     hashed_password: str