Improve error messages

[blaix]

• Specific error(s) for failed queries: Currently, if a request fails due to a bad database query (e.g. a unique constraint fails, you reference a column that doesn't exist, etc), we can't get a helpful error message because of No way to parse response body for HttpClient.BadStatus gren-lang/node#28 - When that issue is fixed, we should parse the error from the response body json. See https://germ.gitbook.io/ws4sqlite/documentation/errors
• Specific error(s) for failed decoding: Currently if decoding fails you get a confusing message about a response body. This comes from the HttpClient failure. To fix this we should probably be decoding to a Value and decode the value separately from the HTTP request.
• Specific error(s) when response JSON includes errors: In certain situations the JSON will be different due to error information in the response. Currently this results in cryptic response json parsing error.
• Specific error(s) when the server is unreachable or returns 4xx/5xx errors (e.g. 404 if you forget to specify the db name in the url).
• It will also help when ws4sql gets error logging so you can at least see the error in the logs.