TableView Cell doesn't occupy full TableView width

Question

I have this tableView in my code which I've set to be have the same leading and trailing as the view which is in it. I can confirm through coloring the background that is working.

Next I created a custom UITableViewCell to populate the tableView, the main element in it is a horizontal stackView which has other elements in it. Everything is working fine except the stackView's width which isn't occupying the entire width of the tableView.

I'm using ViewCode.

The tableView is declared like this in the mainViewController (I know it should be in a View class but it's just a small test project):

private lazy var dailyForecastTableView: UITableView = {
        let table = UITableView()
        table.dataSource = self
        table.backgroundColor = .clear
        table.register(DailyForecastTableViewCell.self, forCellReuseIdentifier: DailyForecastTableViewCell.identifier)
        table.separatorColor = .white
        table.translatesAutoresizingMaskIntoConstraints = false
        return table
    }()

And it's constraints are:

dailyForecastTableView.topAnchor.constraint(equalTo: dailyForecastLabel.bottomAnchor, constant: 16),
            dailyForecastTableView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            dailyForecastTableView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            dailyForecastTableView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor)

As I said, I've colored the background and it is indeed the full width of the screen, this seems to be all fine. The problem seems to be the stack in the tableViewCell:

private lazy var mainCellStackView: UIStackView = {
        let stack = UIStackView(arrangedSubviews: [weekDayLabel, dailyIconImageView, minTemperatureLabel, maxTemperatureLabel])
        stack.axis = .horizontal
        stack.distribution = .fill
        stack.translatesAutoresizingMaskIntoConstraints = false
        stack.isLayoutMarginsRelativeArrangement = true
        stack.directionalLayoutMargins = NSDirectionalEdgeInsets(top: 16, leading: 16, bottom: 16, trailing: 16)
        stack.spacing = 15
        return stack
    }()

The constraints:

private func setupConstraints() {
        mainCellStackView.setConstraintsToParent(contentView)
        
        NSLayoutConstraint.activate([
            mainCellStackView.widthAnchor.constraint(equalTo: contentView.widthAnchor),
            mainCellStackView.centerXAnchor.constraint(equalTo: contentView.centerXAnchor)
        ])
    }

extension UIView {
    func setConstraintsToParent(_ parent: UIView) {
        NSLayoutConstraint.activate([
            self.topAnchor.constraint(equalTo: parent.topAnchor),
            self.leadingAnchor.constraint(equalTo: parent.leadingAnchor),
            self.trailingAnchor.constraint(equalTo: parent.trailingAnchor),
            self.bottomAnchor.constraint(equalTo: parent.bottomAnchor)
        ])
    }
}

If I force the elements inside the stackView to have a larger width the stack occupies more space but the size wouldn't be correct in different phone sizes.

I want the stackView to occupy the entire width of the screen.