Refactor `http.service.ts` error handling

[bastianjoel]

Currently the http.service.ts tries to handle certain backend errors by itself and returns null if it does so.

This is bad because the caller will not be notified properly that a request failed and lacks information about the reasons for that. In case of a password reset which returns null on success it is completely impossible for the caller to determine if the request was successful.

While I think that it is okay to display a snackbar on fail we should change the following things here:

1. Always throw if an error occurred with all information about the response
2. Option to disable opening a snackbar on error

Especially 1. needs testing and maybe some considerations.

[luisa-beerboom]

I think #3217 may have at least partially fulfilled the demands of this issue.
@bastianjoel can you update/close this accordingly?

[jsangmeister]

From my perspective option 2) is sufficently implemented

[bastianjoel]

I still think not throwing an error should not be the default.

From my perspective option 2) is sufficently implemented

I guess you mean 1)?

[bastianjoel]

I will change this to cleanup because the main part is now at least doable.

[jsangmeister]

I guess you mean 1)?

Well, depending on the perspective. I read the option wrong, but the implemented solution comes close to 2). If you set catchError=false, the error will not be caught and no snackbar will be automatically raised.