Serializer should fail on max depth exceeded to break cycles

[noahnu]

Describe the bug

If you serialize an object containing a cycle, it will recurse until call stack overflows / python can no longer handle it, rather than a graceful application error.

To Reproduce

cycle = { "a": {} }
cycle["a"]["b"] = cycle

def test_cycle(snapshot):
    assert snapshot == cycle

Expected behaviour

Error should be thrown if a cycle is detected.

Additional context

We already track "indent". We could add some logic to throw an error if indent exceeds some level as it's essentially equivalent to depth.