IP-895: Option to Initiate Terms When Sending Invoice

[naui95]

See #924 --> must reopen it to re-revert

Description

As indicated in the problem (#895), when sending the invoice, the invoice date and due date are not changed.
Those details are retained as set when the invoice is created, even if changes are made in the period (days, weeks) thereafter.
My solution will always "by default" change the invoice date to the current date and also recalculate the due date, IF the setting [Disable the change of invoice date and due date before emailing] is NOT activated BEFORE SENDING THE EMAIL!
So if the setting is active then the invoice date and due date are NOT changed.

Related Issue

#895

Motivation and Context

For me, this is a problem/rectification that needs to be resolved

#895

Screenshots (if appropriate):

Pull Request Checklist

• My code follows the code formatting guidelines.
• I have an issue ID for this pull request.
• I selected the corresponding branch.
• I have rebased my changes on top of the corresponding branch.

Issue Type (Please check one or more)

• Bugfix
• Improvement of an existing Feature
• New Feature

[nielsdrost7]

@Verony-makesIT reopened the PR, is it still WIP or can we merge it?