HTTP POST to /app for app creation should return HTTP 409 if app already exists

[denismakogon]

HTTP POST to /app for app creation should return HTTP 409 if app already exists, but API service wouldn't do anything rather than accepting request and returning HTTP 200

Steps to reproduce:

1. Create app

curl -H "Content-Type: application/json" -X POST -d '{
    "app": { "name":"myapp" }
}' http://localhost:10501/v1/apps

Response:

{"message":"App successfully created","app":{"name":"myapp","config":null}}

2. Repeat [1]

Response:

{"message":"App successfully created","app":{"name":"myapp","config":null}}

In HTTP v1.1 such case mentioned as HTTP Conflict and server should return corresponding status code HTTP 409.

[ucirello]

I really dispute that 409 is the correct response. First, 4xx are client errors - this is clearly a server-side issue; secondly, assuming that 4xx is the correct error class (which I give in for discussion purposes), I also do not believe 409 is the correct answer. 409 Conflict is to reveal a concurrency problem in competing updates. In this case, we are trying to block a request that shouldn't have taken place anyway - meaning that 400 Bad Request would be a more appropriate response in my opinion.