Service path levels with 0 length should not be allowed

[fgalan]

From https://github.com/telefonicaid/fiware-orion/blob/master/doc/manuals/orion-api.md#entity-service-path

50 maximum characters in each level (1 char is minimum), only alphanumeric and underscore allowed

However, Orion allows creating service path with 0 length levels, eg:

$ curl localhost:1026/v2/entities -vvvv -s -S -H 'Content-Type: application/json' -H 'fiware-servicepath: //detecciondeplagas' -d @- <<EOF
{
  "id": "Room2",
  "type": "Room",
  "temperature": {
    "value": 23,
    "type": "Float"
  },
  "pressure": {
    "value": 720,
    "type": "Integer"
  }
}
EOF

*   Trying 127.0.0.1:1026...
* Connected to localhost (127.0.0.1) port 1026 (#0)
> POST /v2/entities HTTP/1.1
> Host: localhost:1026
> User-Agent: curl/7.88.1
> Accept: */*
> Content-Type: application/json
> fiware-servicepath: //detecciondeplagas
> Content-Length: 148
> 
< HTTP/1.1 201 Created
< Date: Mon, 29 Jan 2024 15:15:25 GMT
< Fiware-Correlator: 3a970da4-beb9-11ee-85a1-080027cd35f1
< Location: /v2/entities/Room2?type=Room
< Content-Length: 0
< 
* Connection #0 to host localhost left intact

[ArqamFarooqui110719]

PR #4503
This PR fixes servicepath levels with zero length, i.e. available in initial part (1st level) of servicepath only (e.g. fiware-servicepath: //det), because servicepath levels with zero length, i.e. available in 2nd level or further level of servicepath (e.g. fiware-servicepath: /a///det), are already restricted by following code in servicePathCheck() function src/lib/rest/rest.cpp file:

    if (compV[ix].c_str()[0] == 0)
    {
      OrionError oe(SccBadRequest, "empty component in ServicePath");
      ciP->answer = oe.setStatusCodeAndSmartRender(ciP->apiVersion, &(ciP->httpStatusCode));
      return 3;
    }