Duplicate OperationIds should be considered invalid

[charjr]

Expected

Calling validate on a \cebe\openapi\spec\OpenApi object containing duplicate operationIds will return false.

Reasoning

OperationIds MUST be unique among all operations described in the API.

Actual

Calling validate on a \cebe\openapi\spec\OpenApi object containing duplicate operationIds returns true.

Example

$api = Reader::readFromJson(<<<JSON
{
 "openapi": "3.0.0",
 "info": {
 "title": "Test API",
 "version": "1.0.0"
 },
 "paths": {
 "/path": {
 "get": {
 "operationId": "op1",
 "responses": {
 "200": {
 "description": "Success"
 }
 }
 },
 "post": {
 "operationId": "op1",
 "responses": {
 "200": {
 "description": "Success"
 }
 }
 }
 }
 }
}
JSON);

var_dump($api->validate()); // bool(true)