feat: Draft through API for Cross-Device Support (#8018)

- Add APIs for cross-device message drafts

ref: #6890

spec/controllers/api/v1/accounts/conversations/draft_messages_controller_spec.rb

@@ -0,0 +1,62 @@
+require 'rails_helper'
+
+RSpec.describe 'Conversation Draft Messages API', type: :request do
+  let(:account) { create(:account) }
+
+  describe 'POST /api/v1/accounts/{account.id}/conversations/<id>/draft_messages' do
+    let(:conversation) { create(:conversation, account: account) }
+    let(:cache_key) { format(Redis::Alfred::CONVERSATION_DRAFT_MESSAGE, id: conversation.id) }
+
+    context 'when it is an unauthenticated user' do
+      it 'returns unauthorized' do
+        get api_v1_account_conversation_draft_messages_url(account_id: account.id, conversation_id: conversation.display_id)
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when it is an authenticated user with access to the inbox' do
+      let(:agent) { create(:user, account: account, role: :agent) }
+      let(:message) { Faker::Lorem.paragraph }
+
+      before do
+        create(:inbox_member, inbox: conversation.inbox, user: agent)
+      end
+
+      it 'saves the draft message for the conversation' do
+        params = { draft_message: { message: message } }
+
+        patch api_v1_account_conversation_draft_messages_url(account_id: account.id, conversation_id: conversation.display_id),
+              params: params,
+              headers: agent.create_new_auth_token,
+              as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(Redis::Alfred.get(cache_key)).to eq(params[:draft_message][:message])
+      end
+
+      it 'gets the draft message for the conversation' do
+        Redis::Alfred.set(cache_key, message)
+
+        get api_v1_account_conversation_draft_messages_url(account_id: account.id, conversation_id: conversation.display_id),
+            headers: agent.create_new_auth_token,
+            as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(response.body).to include(message)
+      end
+
+      it 'removes the draft messages for the conversation' do
+        Redis::Alfred.set(cache_key, message)
+        expect(Redis::Alfred.get(cache_key)).to eq(message)
+
+        delete api_v1_account_conversation_draft_messages_url(account_id: account.id, conversation_id: conversation.display_id),
+               headers: agent.create_new_auth_token,
+               as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(Redis::Alfred.get(cache_key)).to be_nil
+      end
+    end
+  end
+end