public function postBankDetails(Request $request)
    {
        $this->validates(
            $request->all(),
            [
                'account_number' => 'required|accountnumber',
                'sort_code' => 'required|sortcode',
            ]
        );

        $bank_details = Auth::user()->bankDetails ? Auth::user()->bankDetails : new BankDetail;

        $bank_details->accountNumber = $request->input('account_number');
        $bank_details->sortCode = $request->input('sort_code');

        if (!$bank_details->exists) {
            $bank_details->user()->associate(Auth::user());
        }

        $bank_details->save();

        Auth::user()->sendEmail(
            'Your bank details have been changed',
            'emails.account.bank-details-changed'
        );

        return redirect('/account/bank-details')
            ->withStatus('Your bank details have been changed.');
    }