Disable email notification for invoice viewed several times

[meaz]

Akaunting version

3.0.6

PHP version

8.1

Operating system

Debian bullseye

Steps to reproduce

• Create a recurring invoice.
• The invoice is automatically created and sent.
• In your email, check the email saying that an invoice has been created for you and open the provided link.
• Repeat last action several times.

Expected result

• The invoice is marked as "Viewed by the user" in the admin panel only once.
• The admin receives one email letting him know that the user has seen the invoice.

Actual result

• The invoice is marked as "Seen by the user" in the admin panel several times: there are several notifications.
• The admin receives several emails letting him know that the user has seen the invoice.

Additional comments

No response

Relevant log output

No response