feat: support multiple handlers for a single subscription

[jonahsnider]

🔗 Linked issue

Closes #65

❓ Type of change

• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Allows adding multiple handlers to a single channel subscription.
The old API will still work. A new API was added for removing specific handlers without fully unsubscribing from the channel:

const handler1 = () => { /* ... */ };

// start subscription
await redis.subscribe('users/123', handler1);

const handler2 = () => { /* ... */ }; 

// use the existing subscription
await redis.subscribe('users/123', handler2);

// remove handler1, keep subscription alive
await redis.unsubscribe('users/123', handler1);

// no more handlers for channel, close subscription
await redis.unsubscribe('users/123', handler2);

To avoid introducing any breaking changes, the errors in errors.ts were marked @deprecated, since they are no longer relevant with the introduction of this feature.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[RomainLanz]

Hey @jonahsnider! 👋🏻

Sorry for the delay—we totally missed this issue. 😅

I've pushed some changes so the tests can run properly. Now, we just need to update them so they pass with this PR since they were failing before.

Also, I don't think this change is breaking since it adds a feature that wasn't possible before. We throw an error when people tried to do this, so there might be some users expecting that error in their application. What do you think, @thetutlage?

[jonahsnider]

Hey! No worries with the delay, thanks for taking a look now. I just pushed a change to fix the failing tests, let me know if there are more cases that should be added to the suite. Your point about users maybe expecting the error to be thrown is a little spooky, but hopefully that's not a common use case? Would probably be a good idea to add a callout in any release notes just in case.

[thetutlage]

Can we instead write an assertion that both the handlers are being called?

[thetutlage]

Same here?

[thetutlage]

Looks pretty good. Just left a comment to adjust the tests 👍

[jonahsnider]

Looks pretty good. Just left a comment to adjust the tests 👍

Thanks for the review! I just pushed a change which updates the tests based on your feedback. LMK if anything else should be adjusted.

[thetutlage]

Looks good! Thanks for the PR :)

[RomainLanz]

Thanks!