Add channel reads pagination support

[laevandus]

🔗 Issue Links

Resolves: IOS-666

🎯 Goal

Add support for paginating channel reads for accurate read counts in large channels

📝 Summary

Important

Channel reads pagination is only supported through channel query endpoint while paginating members (slightly hidden feature)

• Use channel query endpoint in Chat.loadMembers(with:) and Chat.loadMoreMembers(limit:) which also paginates channel reads for these members
• Update ChannelQuery to support setting pagination parameter for members
• Do not reset ChannelDTO.reads when saving channel payloads, only reset it when loading the first page of messages using the same endpoint (aka ChatChannelController.synchronize or Chat.get(watch:))
• Recalculate MessageDTO.readBy for existing messages when saving channel payloads
• Add demo app debug command for loading more members

🛠 Implementation

We use ChatMessage.readBy for showing read counts for current user's messages. This property is updated using ChannelDTO.reads (manual filtering). Channel reads are fetched based on requested channel members and by default up to 100 channel members are fetches (and reads for these users). If there are many members and we would like to get accurate channel reads, we would need to paginate members using channel query endpoint (members endpoint does not give channel reads).
Chat already incorporates member pagination. Before it was using /members endpoint, but this PR changes it to use the channel query endpoint.
End result is that creating an instance of Chat and calling get(watch:) will automatically give access to channel members fetched using the regular channel query call (default is 100 members and their channel reads). If we want more, we just need to call loadMoreMembers(limit:) and we get next page of members and their channel read information.

let chat = client.makeChat(for: cid)
try await chat.get(watch: true)
let members = chat.state.members // first page, 100
let reads = chat.state.channel?.reads // first 100, `ChatMessage.readBy` is updated based on 100 reads
try await chat.loadMoreMembers(limit: 100)
let members2 = chat.state.members // 200
let reads2 = chat.state.channel?.reads // 200, `ChatMessage.readBy` is updated based on 200 reads

Open questions

1. Should we paginate channel reads automatically in UI components? Config option? Gives accurate read receipts.

🎨 Showcase

🧪 Manual Testing Notes

☑️ Contributor Checklist

• I have signed the Stream CLA (required)
• This change should be manually QAed
• Changelog is updated with client-facing changes
• Changelog is updated with new localization keys
• New code is covered by unit tests
• Documentation has been updated in the docs-content repo

[Stream-SDK-Bot]

SDK Performance

target	metric	benchmark	branch	performance	status
MessageList	Hitches total duration	10 ms	3.34 ms	66.6% 🔼	🟢
	Duration	2.6 s	2.56 s	1.54% 🔼	🟢
	Hitch time ratio	4 ms per s	1.3 ms per s	67.5% 🔼	🟢
	Frame rate	75 fps	78.78 fps	5.04% 🔼	🟢
	Number of hitches	1	0.4	60.0% 🔼	🟢

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
StreamChat	7.4 MB	7.41 MB	+17 KB	🟢
StreamChatUI	4.78 MB	4.78 MB	0 KB	🟢

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
98.8% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud