"POST /terms" error message when "legacyId" in not unique

[maxceem]

At the moment if we try to create a new "TermsOfUse" record and send legacyId which is already in use, server would return error with status 500:

{
    "message": "Internal server error"
}

It's hard to understand what is wrong with request from this error message.

It would be better to return some particular error message with status 400, like:

{
    "message": "TermsOfUse with such 'legacyId' already exists. It should be unique."
}