Make error codes consistent

[JohannesOehm]

For example, in websocket_api.ts, errors are handled as follows (line 389):

console.error(
"dataError",
`There was en error executing the procedure [code: 3]: (${procedureName}) ${error}`
)

this.saveToCache(
undefined,
// { data: undefined },
payload,
"raw_data",
procedureName,
error
)
client.emit(
"dataError",
`There was en error executing the procedure [code: 2]: ${error}`
)

As you can see, there is a different error code written to the command line then the error code submitted to the client. This leads the user to the impression, that there are different error codes. Please fix.