feat: add custom events to Relay

[weboko]

Problem

There was a report that Relay.observers were not properly cleaned up and it was hard to debug in a runtime so some hack was introduced on the consumer side.

Solution

Add observer:added and observer:removed to track state of the internal observers structure.

Notes

• Resolves Relay interface doesn't include 'observers' #1142

Validation

[fryorcraken]

Looks good. I only wonder if we should use CustomEvents from libp2p or have our own. The event does not seem libp2p related so just wonder if we are restricting ourselves here.

[weboko]

Looks good. I only wonder if we should use CustomEvents from libp2p or have our own. The event does not seem libp2p related so just wonder if we are restricting ourselves here.

Not really, CustomEvent is just a browser abstract and we can avoid using it altogether any time even now.
Used it just to be consistent with GossipSub

[fryorcraken]

Looks good bug I wonder if it's good enough for @therealjmj. We might need a dump function too.

[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
Waku core	116.74 KB (+0.03% 🔺)	2.4 s (+0.03% 🔺)	992 ms (-11.49% 🔽)	3.4 s
Waku default setup	384.04 KB (+0.02% 🔺)	7.7 s (+0.02% 🔺)	2.3 s (-6.69% 🔽)	10 s
ECIES encryption	27.99 KB (0%)	560 ms (0%)	387 ms (-22.48% 🔽)	947 ms
Symmetric encryption	27.99 KB (0%)	560 ms (0%)	501 ms (+12.07% 🔺)	1.1 s
DNS discovery	108.07 KB (0%)	2.2 s (0%)	1.2 s (+13.64% 🔺)	3.3 s
Privacy preserving protocols	116.22 KB (+0.03% 🔺)	2.4 s (+0.03% 🔺)	922 ms (-9.74% 🔽)	3.3 s
Light protocols	117.98 KB (+0.03% 🔺)	2.4 s (+0.03% 🔺)	961 ms (+14.95% 🔺)	3.4 s
History retrieval protocols	118.06 KB (+0.03% 🔺)	2.4 s (+0.03% 🔺)	746 ms (-7.84% 🔽)	3.2 s

[therealjmj]

Looks good bug I wonder if it's good enough for @therealjmj. We might need a dump function too.

Funny, in making 'observers' private, it's likely this broke our implementation.
We just want a way to log the current observers, as you say, a "dump".

[weboko]

@therealjmj I can followup with a "dump" function but isn't it enough to have these two events for you to track what happens to observers? If you have a need for full observers list it can be maintained by these events too.

[therealjmj]

@therealjmj I can followup with a "dump" function but isn't it enough to have these two events for you to track what happens to observers? If you have a need for full observers list it can be maintained by these events too.

I'm really not a fan of events and listener/subscriber models - it'll add tech that needs to be tested and maintained on our end.

However... I would love a "dump" function to make it much easier on us!

[weboko]

Ok :) Adding dump function soon

upd: added here #1249