[Bug] Review New Terms Schema and Transform Method Regarding JSONSchema

[terrancedejesus]

Describe the bug
Based on discussion from community, when uploading rules view the CLI command, it references the JSONschema which is a frozen state of the NewTermsRuleData schema.

In the NewTermsRuleData class there is a method called transform which is called if it exists from _post_dict_conversion. This method, for NewTermsRuleData specifically adjusted the JSON object of the New Terms rule so that new_terms becomes new_terms_fields and sits in the root of the JSON object. This is the expected format of the rule object for the Kibana API.

The reason the schema was developed this way was based on how rule types and schemas are identified by the rule loader, which will attempt to find new_terms which is what type is set to in a TOML rule.

Since the JSONSchema is frozen based on the NewTermsRuleData when it attempts to validate the API object of the rule, the fields are not matching and thus causes issues when jsonschema.validate() is called during strip_additional_properties which is used when attempting to upload rules from CLI.

def strip_additional_properties(version: Version, api_contents: dict) -> dict:
    """Remove all fields that the target schema doesn't recognize."""

    if Version.parse(version, optional_minor_and_patch=True) >= Version.parse("8.3.0"):
        api_contents = strip_build_time_fields(api_contents)

    stripped = {}
    target_schema = get_schema_file(version, api_contents["type"])

    for field, field_schema in target_schema["properties"].items():
        if field in api_contents:
            stripped[field] = api_contents[field]

    # finally, validate against the json schema
    jsonschema.validate(stripped, target_schema)
    return stripped

To Reproduce

1. Go to an old branch in our repo
2. Use a later stack version than the repo selected
3. Run the upload-rule command
4. See that any new terms rule either error or have been removed from the upload because of jsonschema validation

Additional Information

Please see #2360