Feat/error handling

[weiseng18]

Problem

1. The generic throw new Error was previously used, so all errors are 500. In the two locations it is used, a 400 should be thrown instead.
2. The frontend page /matrix was not able to access the actual custom error message, instead it just says Request failed with status code 500

Solution

1. Create a HttpException class that accepts a status code to throw non-500 errors easily, and update the two locations to throw a 400 instead.
2. The actual error is located in err.response.data.message, and not err.message. Update the line

Checklist

• If the branch was not created off latest develop, merge locally
• Using latest develop and master, do git diff --stat master while in develop branch. Ensure that the diff is not too large

Notes

Considered writing a middleware to handle the errors, but that would require next() which is not part of Vercel's serverless functions structure. I could use next: Function, and it would work as expected. However, the API tests use vercel-node-server, which is not able to trigger next(), and rightfully so since it is not part of Vercel's serverless functions structure.

[vercel]

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