Default values over merged schemas

Hello,
I'm trying to build a mechanism to versioning default values for my app over ajv backed separated JSON files.

### TL; DR:
I couldnt generate default values from a merged schema. Please elaborate on what i'm missing or doing wrong.

### Details:
You can find the sandbox [here](https://codesandbox.io/s/immutable-wind-yv72w?file=/src/App.js)

My concerns are:
- Use default values and validate the data only related props according to the version
- Use v0 as a base JSON and struct upcoming versions via $merge/$patch keywords (Dont repeat unchanged props and definitions)
- Use a separeted common definitions JSON file to feed the base or merged/patched schemas.

A simple example goes like this:

/schemas/v0/App.json:
```
{
"$schema": "http://json-schema.org/draft-07/schema#",
"$id": "https://some.domain.com/schemas/v0/App.json#",
"title": "App Schema v0",
"description": "App Properties",
"type": "object",
"additionalProperties": false,
"definitions": {
"yesNo": {
"$ref": "https://some.domain.com/schemas/commonDefinitions.json#/definitions/yesNo"
},
"description": {
"$ref": "https://some.domain.com/schemas/commonDefinitions.json#/definitions/description"
},
"color": {
"$ref": "https://some.domain.com/schemas/commonDefinitions.json#/definitions/color"
},
"URL": {
"$ref": "https://some.domain.com/schemas/commonDefinitions.json#/definitions/color"
}
},
"properties": {
"appVersion": {
"type": "string",
"const": "0",
"default": "0"
},
"appBgColor": {
"$ref": "#/definitions/color",
"description": "App bg color",
"default": "#ffffff"
},
"name": {
"type": "string",
"default": "New App"
},
"description": {
"$ref": "#/definitions/description",
"default": "my app"
},
"logoURL": {
"$ref": "#/definitions/URL",
"description": "Logo asset URL",
"default": "https://source.unsplash.com/random/50x50"
}
},
"required": ["appVersion"]
}

```
/schemas/v1/App.json:
```
{
"$schema": "http://json-schema.org/draft-07/schema#",
"$id": "https://some.domain.com/schemas/v1/App.json#",
"$merge": {
"source": {
"$ref": "https://some.domain.com/schemas/v0/App.json#"
},
"with": {
"properties": {
"appVersion": {
"const": "1",
"default": "1"
},
"showItemIcons": {
"$ref": "#/definitions/yesNo",
"default": "Nope"
}
}
}
}
}
```
/schemas/commonDefinitions.json:
```
{
"$schema": "http://json-schema.org/draft-07/schema#",
"$id": "https://some.domain.com/schemas/commonDefinitions.json#",
"title": "App Schema Common Definitions",
"description": "Common Definitions",
"type": "object",
"additionalProperties": false,
"definitions": {
"yesNo": {
"type": "string",
"enum": ["Yes", "No"]
},
"alignment": {
"type": "string",
"enum": ["left", "center", "right"]
},
"description": {
"type": "string",
"maxLength": 5
},
"color": {
"type": "string"
},
"URL": {
"type": "string"
},
"empty": {
"type": "string",
"maxLength": 0
}
}
}
```
I couldn't make ajv to produce correct data with defaults on v1/App.json:
```
{}
```
However it's ok for v0/App.json:
```
{"appVersion":"0","appBgColor":"#ffffff","name":"New App","description":"my app","logoURL":"https://source.unsplash.com/random/50x50"}

```

Additional problems:
- It seems validation ignore default values. See v0/App.json#properties.description shouldn't exceed 5 length value. But validator tells it's valid for 'my app'.
- I couldn't make codesandbox work by referencing relatively within schemas. Is it ok to access other schemas as:
```
{
"$schema": "http://json-schema.org/draft-07/schema#",
"$id": "https://www.jotform.com/portal/schemas/v1/App.json#",
"$merge": {
"source": {
"$ref": "../v0/App.json"
},
"with": {
......
}
}
```
- And finally please see that i need 'yesNo' definition starting from v1. However it seems it needs to be defined in also v0. I got `MissingRefError`s if i dont include it to v0. What is the correct way to extend `definitions` and `required`?