Fix(ParticipantsStore): Purge the store so it deletes the removed conversation

[DorraJaouad]

☑️ Resolves

• Fix Quirks joining an open conversation #11101

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After

🚧 Tasks

• Code review

🏁 Checklist

• 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

[DorraJaouad]

/backport to stable28

[Antreesy]

Half of the problem solved =)

If open conversation was cached, then you left and reload a page, BrowserStorage still keeps it for you, and on reload populates participantsStore again.

Let's add this line to the end of action:
context.dispatch('cacheConversations')

spreed/src/store/conversationsStore.js

Lines 323 to 329 in 869e44c

	deleteConversation(context, token) {
	// FIXME: rename to deleteConversationsFromStore or a better name
	const chatExtrasStore = useChatExtrasStore()
	chatExtrasStore.purgeChatExtras(token)
	context.dispatch('deleteMessages', token)
	context.commit('deleteConversation', token)
	},

[Antreesy]

Tested when leaving conversation, deleting self, and deleted by moderator. Purged and cached correctly