Add APIs for updating Git manager from A+

[ihalaij1]

Description

What?

Added some APIs to support new Git manager entries being created/edited from A+.

Why?

These changes were needed in order to implement Git manager settings and cloning in A+.

Testing

What type of test did you run?

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

Tested that the new code works as expected when calling from A+.

Did you test the changes in

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

Translation

• [ ] 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?
• [ ] 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?

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

[ihalaij1]

I made the requested changes!