@spec lenient_fetch(map(), atom()) :: {:ok, term()} | :error

Fetches key from map, accepting either the atom key or its string form.

The HTTP layer decodes JSON to atom keys, but a body we re-decoded locally has string keys — so try the atom first, then fall back to the string.

@spec snake_case_keys(map()) :: map()

Recursively rewrites a map's camelCase keys (atom or string) into snake_case string keys, descending into nested maps and lists.

Bridges the Gamma API's camelCase payloads to our snake_case schema fields.

iex> Polymarket.JsonUtil.snake_case_keys(%{conditionId: "0x1", feeSchedule: %{rebateRate: 0.2}})
%{"condition_id" => "0x1", "fee_schedule" => %{"rebate_rate" => 0.2}}