Presence docs to discourage building of presence sets

[mattheworiordan]

A partner of ours has been building an app which has erratic presence behaviour. Upon inspecting the code, we see the same pattern of developers continuing to try and build their own presence sets based on enter, leave, update events, which is flawed and should never be done, they should instead rely on the presence get method to get the complete presence set. We suffered this same issue ourselves with our Spaces SDK development. If our own internal staff are making these mistakes, and partners are making these mistakes, customers will certainly be making these mistakes.

Here is the sample code for ref:

We really need to rethink our presence docs to encourage the right behaviours. When I read https://ably.com/docs/presence-occupancy/presence, I see no mention of why users should not handle enter, leave, update events and build their own presence set, and in fact the get method to get the presence set only appears a couple of (virtual) pages down the page.

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