get data version

// api get content
// url /api/control_versions/data_control_version/content/?blah=blah

// request param : (content_type, content_id) หรือ (data_version_id)

// response case no course, no data version
{
    "schema_version_id": 1,
    "data_version_id": null,
    "version_number": null,
    "is_published": False,
    "last_published": null,
    "raw_data": {},
    "content_type": null,
    "content_id": null
}

// response case course, data version
{
    "schema_version_id": 1,
    "data_version_id": 1,
    "version_number": 0.1,
    "is_published": False,
    "last_published": null,
    "raw_data": {"blah": "blah"},
    "content_type": "course",
    "content_id": 33
}

// response case no course, data version
{
    "schema_version_id": 1,
    "data_version_id": 1,
    "version_number": 0.1,
    "is_published": False,
    "last_published": null,
    "raw_data": {"blah": "blah"},
    "content_type": "course",
    "content_id": null
}