[BUG][dart-dio] property with type `AnyValue` ignores the `default` parameter

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Consider the following property schema:

"fooPropC": {
  "default": "some default value"
},

or

"fooPropC": {
  "type": "AnyValue",
  "default": "some default value"
},

the default parameter here is completely ignored:

{
  "openApiType": "AnyType",
  "baseName": "fooPropC",
  "complexType": "JsonObject",
  "getter": "getFooPropC",
  "setter": "setFooPropC",
  "dataType": "JsonObject",
  "datatypeWithEnum": "JsonObject",
  "name": "fooPropC",
  "defaultValueWithParam": " = data.fooPropC;",
  "baseType": "JsonObject",
  "example": "null",
  "jsonSchema": "{\n  \"type\" : \"AnyType\"\n}",
  "exclusiveMinimum": false,
  "exclusiveMaximum": false,
  "required": false,
  "deprecated": false,
  "hasMoreNonReadOnly": false,
  "isPrimitiveType": false,
  "isModel": false,
  "isContainer": false,
  "isString": false,
  "isNumeric": false,
  "isInteger": false,
  "isShort": false,
  "isLong": false,
  "isUnboundedInteger": false,
  "isNumber": false,
  "isFloat": false,
  "isDouble": false,
  "isDecimal": false,
  "isByteArray": false,
  "isBinary": false,
  "isFile": false,
  "isBoolean": false,
  "isDate": false,
  "isDateTime": false,
  "isUuid": false,
  "isUri": false,
  "isEmail": false,
  "isNull": false,
  "isFreeFormObject": false,
  "isAnyType": false,
  "isArray": false,
  "isMap": false,
  "isEnum": false,
  "isInnerEnum": false,
  "isReadOnly": false,
  "isWriteOnly": false,
  "isNullable": false,
  "isSelfReference": false,
  "isCircularReference": false,
  "isDiscriminator": false,
  "vars": [],
  "requiredVars": [],
  "vendorExtensions": {
    "x-index": 3
  },
  "hasValidation": false,
  "isInherited": false,
  "nameInCamelCase": "FooPropC",
  "nameInSnakeCase": "FOO_PROP_C",
  "uniqueItems": false,
  "isXmlAttribute": false,
  "isXmlWrapped": false,
  "additionalPropertiesIsAnyType": false,
  "hasVars": false,
  "hasRequired": false,
  "hasDiscriminatorWithNonEmptyMapping": false,
  "hasMultipleTypes": false,
  "schemaIsFromAdditionalProperties": false,
  "datatype": "JsonObject",
  "iexclusiveMaximum": false,
  "hasItems": false
}

this is probably a bug with the core generator, since the raw schema doesn't include the default parameter "jsonSchema": "{\n \"type\" : \"AnyType\"\n}",

openapi-generator version

latest master: 6.3.0

@jaumard (2018/09) @josh-burton (2019/12) @amondnet (2019/12) @sbu-WBT (2020/12) @kuhnroyal (2020/12) @agilob (2020/12) @ahmednfwela (2021/08) @wing328

Reproduce the issue with the two provided schemas and inspect the OpenAPI Generator core path that builds the property metadata shown in the report. Trace why the default is absent from the raw schema for an AnyValue property, then verify that generated dart-dio output preserves the default value.