[API] Enable to enrich function with node selection attributes on job submission endpoint

[Hedingber]

Adding support to providing node selection attributes on job submission request body to enrich the function, example body attached, notes:

• The fields in affinity are the same as the k8s object (details here)
• There is a technical limitation enforcing the affinity inner structure to be camelCase (and not snake_case as the rest of our API)

{
        "task": {...},
        "function": {
            "spec": {
                "node_name": "k8s-node1",
                "node_selector": {"kubernetes.io/hostname": "k8s-node1"},
                "affinity": {
                    "nodeAffinity": {
                        "preferredDuringSchedulingIgnoredDuringExecution": [
                            {
                                "preference": {
                                    "matchExpressions": [
                                        {
                                            "key": "some_node_label",
                                            "operator": "In",
                                            "values": [
                                                "possible-label-value-1",
                                                "possible-label-value-2",
                                            ],
                                        }
                                    ]
                                },
                                "weight": 1,
                            }
                        ],
                        "requiredDuringSchedulingIgnoredDuringExecution": {
                            "nodeSelectorTerms": [
                                {
                                    "matchExpressions": [
                                        {
                                            "key": "some_node_label",
                                            "operator": "In",
                                            "values": [
                                                "required-label-value-1",
                                                "required-label-value-2",
                                            ],
                                        }
                                    ]
                                }
                            ]
                        },
                    },
                    "podAffinity": {
                        "requiredDuringSchedulingIgnoredDuringExecution": [
                            {
                                "labelSelector": {
                                    "matchLabels": {
                                        "some-pod-label-key": "some-pod-label-value"
                                    }
                                },
                                "namespaces": ["namespace-a", "namespace-b"],
                                "topologyKey": "key-1",
                            }
                        ]
                    },
                    "podAntiAffinity": {
                        "preferredDuringSchedulingIgnoredDuringExecution": [
                            {
                                "podAffinityTerm": {
                                    "labelSelector": {
                                        "matchExpressions": [
                                            {
                                                "key": "some_pod_label",
                                                "operator": "NotIn",
                                                "values": [
                                                    "forbidden-label-value-1",
                                                    "forbidden-label-value-2",
                                                ],
                                            }
                                        ]
                                    },
                                    "namespaces": ["namespace-c"],
                                    "topologyKey": "key-2",
                                },
                                "weight": 1,
                            }
                        ]
                    },
                },
            }
        },
    }

Implements: https://jira.iguazeng.com/browse/ML-530