consistent alerting

[steveklebanoff]

• don't set block as alerted if it failed to run
• check to see if already alerted on before alerting

[marcusmolchany]

one comment for a cache key helper. this change is great

[marcusmolchany]

super nit but we could make something like:

const getAlertedCacheKey = (type: "discord" | "twitter", txHash: string): string =>
  `alerted:${type}:${txnHash.toLowerCase()}`;

and then this could be

Suggested change

	await setRedisAsync(`alerted:${type}:${txnHash.toLowerCase()}`, "true");
	const cacheKey = getAlertedCacheKey(type, txnHash);
	await setRedisAsync(cacheKey, "true");