chore: Review HTTP support codes

[ChrisBQu]

Relevant issue(s)

Resolves #3139

Description

Across the code base we sometimes use http.StatusBadRequest (400) where we should be using http.StatusInternalServerError (500). I have gone through the code and made some of the changes that made logical sense to me.

Tasks

• I made sure the code is well commented, particularly hard-to-understand areas.
• I made sure the repository-held documentation is changed accordingly.
• I made sure the pull request title adheres to the conventional commit style (the subset used in the project can be found in tools/configs/chglog/config.yml).
• I made sure to discuss its limitations such as threats to validity, vulnerability to mistake and misuse, robustness to invalidation of assumptions, resource requirements, ...

How has this been tested?

Specify the platform(s) on which this was tested:

• Windows

[AndrewSisley]

question: Why is this a draft PR?

[ChrisBQu]

question: Why is this a draft PR?

I forgot to change it! I try to always create my PRs as drafts, then adjust them when I'm ready. I just forgot here.

[AndrewSisley]

I forgot to change it! I try to always create my PRs as drafts, then adjust them when I'm ready. I just forgot here.

Ah okay 😁

[AndrewSisley]

thought: I'm not sure these are all correct - many of these errors returned could be user input errors, in which case BadRequest would be appropriate no?