Which is the better way of relating these database tables? - postgresql

Question

I have a table Users and Matters. Ordinarily only admins can create a matter so I did a one to many relationship between users and matters(User.hasMany(Matter)) and (Matter.belongsTo(User))
Now on the frontend, Matter is supposed to have a multi-select field called assignees where users gotten from the User table can be selected.
My current approach is to make assignees a column on Matter which will be an array of user emails selected on the frontend but the frontend developer thinks I should make it an array of user ids instead but I think that won't be efficient because when getting all matters or updating them, one will need to run a query each time to get the associated assignees using the array of ids stored in the assignees column(and I am not entirely sure on how to go about that).
Another option is having a UserMatters join table but I don't think it will be performant-friendly to populate two tables(Matter and UserMatters) on creation of a matter while updating and getting all matters will involve writing lots of code.
My question is, is there a better way to go about this or should I just stick with populating the assignees field with user emails since it looks like a better approach as far as I can see?
N.B: I am using sequelize(postgres)

Answer 1

So what I did was instead of creating a through/join table, the frontend sent an array of integers containing the IDs of the assignees. Since the assignees are also users on the app, when I get a particular matter, I just loop through the IDs in the assignees column which is an array and get the user details from the user table then I reassign the result to that column and return the resource.
try {
// get the resource
const resource = await getResource(id);
/*looping through the column containing an array of IDs and converting it to numbers(if they are strings)**/
let newArr = resource.assignees.map(id => Number(id));
let newAssignees;
/**fetch all users with the corresponding IDs and wait for that process to be complete**/
newAssignees = await Promise.all(newArr.map(id => getUserById(id)));
/**Returns only an array of objects(as per sequelize)**/
newAssignees.map(el => el.get({ raw: true }));
/**reassign the result**/
resource.assignees = newAssignees;
if(resource)
return res.status(200).json({
status: 200,
resource
})
} else {
return res.status(404).json({
status: 404,
message: 'Resource not found'
});
}
} catch(error){
return res.status(500).json({
status: 500,
err: error.message
})
}