Redirect back to form after adding or removing deviations

[Mikael-Lenander]

Description

What?

After adding or removing a deadline or submission deviation through the form, redirects back to the form instead of redirecting to the deviation list page.

Why?

The deviation lists load very slowly, especially in courses with many deviations like Programming 1. This is just a way to avoid visiting the deviation page. This mainly concerns the deadline deviation list but I added the same modifications to submission deviations as well for consistency.

How?

Changes the success urls of views.

Fixes #1122 (partly)

Testing

Remember to add or update unit tests for new features and changes.

• How to test your changes in A-plus
• How to test accessibility

What type of test did you run?

• [ ] Accessibility test using the WAVE extension.
• [x] Django unit tests.
• [x] Selenium tests.
• [ ] Other test. (Add a description below)
• [x] Manual testing.

Added, overrode and removed deadline and submission deviations through the web interface.

Did you test the changes in

• [ ] Chrome
• [x] Firefox
• [ ] This pull request cannot be tested in the browser.

Think of what is affected by these changes and could become broken

Translation

• [x] Did you modify or add new strings in the user interface? (Read about how to create translation)

Programming style

• [x] Did you follow our style guides?
• [x] Did you use Python type hinting in all functions that you added or edited? (type hints for function parameters and return values)

Have you updated the README or other relevant documentation?

• [ ] documents inside the doc directory.
• [ ] README.md.
• [ ] Aplus Manual.
• [ ] Other documentation (mention below which documentation).

Is it Done?

• [ ] Reviewer has finished the code review
• [ ] After the review, the developer has made changes accordingly
• [ ] Customer/Teacher has accepted the implementation of the feature

Clean up your git commit history before submitting the pull request!