PIN-7241 - Fix bad request body in authorization-server

[shuyec]

Related Jira tickets: PIN-7241, PIN-7244, PIN-7308

This PR fixes the error message which gets returned when calling the authorization-server endpoint with a bad formatted request JSON body.
Examples:

• { -> Expected property name or '}' in JSON at position 7 (line 1 column 8)
• test -> Unexpected token 't', "test" is not valid JSON
• {"test":"test" -> Expected ',' or '}' after property value in JSON at position 14 (line 1 column 15)

The PR changes the error to:

{
  "type": "about:blank",
  "title": "Bad request",
  "status": 400,
  "detail": "Expected property name or '}' in JSON at position 1 (line 1 column 2)",
  "errors": [
    {
      "code": "000-9999",
      "detail": "Expected property name or '}' in JSON at position 1 (line 1 column 2)"
    }
  ]
}

[shuyec]

.message adds Expected property name or '}' in JSON at position 1 (line 1 column 2) which is not very clean, but it's descriptive of what's happening.
It could be changed to an Unexpected error message.

[Carminepo2]

z.ZodError is also a instance of Error. So this will always end up on the first branch of the ternary.
body-parser throws a SyntaxError, I would check for it

[shuyec]

I can change that to SyntaxError, but, from my understanding, Zod parsing errors are handled by this.