feat(schema): list schema api

[thegeekywanderer]

An endpoint for listing all schemas for a tenant with a paginated response.
Here's the response body:

{
    "head": "<head_version>",
    "schemas": [
        {
            "version": "<version-1>",
            "created_at": "<timestamp>"
        },
        {
            "version": "<version-2>",
            "created_at": "<timestamp>"
        },
    ],
    "continuous_token": ""
}