support custom fingerprint generation

[mahendraHegde]

currently fingerprint is generated based on body, it should be customisable.
current logic:

node-idempotency/packages/core/src/idempotency.ts

Lines 105 to 109 in 21d260a

	private getFingerPrint(
	req: IdempotencyParamsWithDefaults,
	): string | undefined {
	return req.body ? this.hash(req.body) : undefined;
	}

similar to skipRequest add an option to generate fingerprint and use the option or default(current approach) for fingerprint generation.