🧹 Replace 403 by 401 in some occurences

[Annelein]

Fixes #3634

How to test
Not really possible I think, but all unit tests should pass of course.

[Annelein]

@Felienne

• I wasn't sure about some 403's, so I commented on them, can you let me know if these should be 401's?
• some errors that I changed to 401's, have different error messages then, "unauthorized", for example all occurrences in statistics.py. Should these error messages be changed to "unauthorized"?
• I will of course fix the unittests after I know for sure that these are the correct error responses!

[Felienne]

@Felienne

• I wasn't sure about some 403's, so I commented on them, can you let me know if these should be 401's?
• some errors that I changed to 401's, have different error messages then, "unauthorized", for example all occurrences in statistics.py. Should these error messages be changed to "unauthorized"?
• I will of course fix the unittests after I know for sure that these are the correct error responses!

Pinging @TiBiBa (or otherwise maybe @rix0rrr or @jpelay here) I did not make this issue and I am not really an expert in this actually :)

[jpelay]

Hi @Annelein I commented on each case that I saw a comment of yours, hope it helped!

[jpelay]

some errors that I changed to 401's, have different error messages then, "unauthorized", for example all occurrences in statistics.py. Should these error messages be changed to "unauthorized"?

I think that it's fine to have some more descriptive error messages than just a generic one.

[jpelay]

Great job!

[mergify]

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