Chore: Refactor round robin logic (#1015)

Co-authored-by: Pranav Raj S <pranav@thoughtwoot.com>

spec/models/conversation_spec.rb

@@ -108,6 +108,7 @@ RSpec.describe Conversation, type: :model do
     end
 
     before do
+      create(:inbox_member, inbox: inbox, user: agent)
       allow(Redis::Alfred).to receive(:rpoplpush).and_return(agent.id)
     end
 
@@ -141,9 +142,11 @@ RSpec.describe Conversation, type: :model do
       conversation.status = 'resolved'
       conversation.save!
       expect(conversation.reload.assignee).to eq(agent)
+      inbox.inbox_members.where(user_id: agent.id).first.destroy!
 
       # round robin changes assignee in this case since agent doesn't have access to inbox
       agent2 = create(:user, email: 'agent2@example.com', account: account)
+      create(:inbox_member, inbox: inbox, user: agent2)
       allow(Redis::Alfred).to receive(:rpoplpush).and_return(agent2.id)
       conversation.status = 'open'
       conversation.save!