Add more info about max_points to points API

[etanttila]

Description

What? Add fields max_points and max_points_by_difficultyto the points API general information. This simplifies calculating relevant points in MOOC-Jutut. The max_points field was already provided in the API for modules, but not for the course as a whole, and the max points for each category/difficulty weren't in the API beforehand.

Why?

So viewing points via Jutut could work more efficiently

How?

Adding the fields max_points and max_points_by_difficulty to the API

Fixes #

Testing

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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 locally that they appear in the API and the change works with the Jutut pull request

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

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• [ ] 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

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