Add a way to send using custom code when dropping files/folders

[Jacalz]

Checklist

• [X] I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• [X] This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

The (upcoming) v3.5.0 release adds support for dropping file and folders onto the window but there is currently no way to use custom codes for the send.

Describe the solution you'd like to see.

We need to think of a good way to make it possible to specify using custom codes when dropping files. How to expose that is a good question.

[GalihFajar]

Hi @Jacalz I've made a draft PR to address this issue. Made it as a draft because it's still an idea (+ contains no new added tests). Please find the PR description to see how it works.

Thanks.

[Jacalz]

Thanks @GalihFajar. I appreciate you taking the time to contribute. I'll have a look later today :)

PS: You can skip the tests if you want. I haven't quite set up a good plan for how I want to handle tests for the backend and some code might have to be refactored to be more easily testable. It has been a longstanding plan of mine to make sure to add more tests.

[Jacalz]

Thanks @GalihFajar. This is now solved.