Add a JSON schema describing the packages install structure

Since the structure we're setting in place for installing packages has
some complexity, add a JSON schema to avoid frustrating errors when
modifying the informations (adding/removing packages install).

roles/kubernetes/preinstall/files/pkgs-schema.json

@@ -0,0 +1,75 @@
+{
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "$id": "https://kubespray.io/internal/os_packages.schema.json",
+    "title": "Os packages",
+    "description": "Criteria for selecting packages to install on Kubernetes nodes during installation by Kubespray",
+    "type": "object",
+    "patternProperties": {
+        ".*": {
+            "type": "object",
+            "additionalProperties": false,
+            "properties": {
+                "groups": {
+                    "description": "Match if the host is in one of these groups. If not specified match any host.",
+                    "type": "array",
+                    "minItems": 1,
+                    "items":{
+                        "type": "string",
+                        "pattern": "^[0-9A-Za-z_]*$"
+                    }
+                },
+                "os": {
+                    "type": "object",
+                    "description": "If not specified match any OS. Otherwise, must match by 'families' or 'distributions' to be included.",
+                    "additionalProperties": false,
+                    "minProperties": 1,
+                    "properties": {
+                        "families": {
+                            "description": "Match if ansible_os_family is part of the list.",
+                            "type": "array",
+                            "minItems": 1,
+                            "items": {
+                                "type": "string"
+                            }
+                        },
+                        "distributions": {
+                            "type": "object",
+                            "description": "Match if ansible_distribution match one of defined keys.",
+                            "minProperties": 1,
+                            "patternProperties": {
+                                ".*": {
+                                    "description": "Match if either the value is the empty hash, or one major_versions/versions/releases contains the corresponding variable ('ansible_distrbution_*')",
+                                    "type": "object",
+                                    "additionalProperties": false,
+                                    "properties": {
+                                        "major_versions": {
+                                            "type": "array",
+                                            "minItems": 1,
+                                            "items": {
+                                                "type": "string"
+                                            }
+                                        },
+                                        "versions": {
+                                            "type": "array",
+                                            "minItems": 1,
+                                            "items": {
+                                                "type": "string"
+                                            }
+                                        },
+                                        "releases": {
+                                            "type": "array",
+                                            "minItems": 1,
+                                            "items": {
+                                                "type": "string"
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}