SchemaVer works with remote references

[widal001]

User stories

As someone generating releases using schema, I want schemaver to load/check remote schemas linked via the "$ref" attribute, so that I can accurately categorize changes made between referenced schemas.

Acceptance criteria

Assuming we have the following schemas we want to compare:

Old schema

{
    "type": "object",
    "properties": {
         "productId": {"type": "integer"},
         "productName": {"type": "string"},
         "tags": {"$ref": "https://example.com/tags/2023-01-01.json"},
    },
    "required": ["productId", "productName", "tags"]
}

New schema

{
    "type": "object",
    "properties": {
         "productId": {"type": "integer"},
         "productName": {"type": "string"},
         "tags": {"$ref": "https://example.com/tags/2024-01-03.json"},
    },
   "required": ["productId", "productName", "tags"]
}

And the two remote schemas referenced are:

.../tags/2023-01-01.json

{
    "type": "array",
    "items": {"type": "string"}
}

.../tags/2024-01-03.json

{
    "type": "array",
    "items": {
        "type": "object",
        "properties": {
            "label": {"type": "string"},
            "tagId": {"type": "integer"}
        }
    }
}

The resulting release should have type model