feat: Ability to search conversation with message content (#1265)

- API end point which takes message content as search parameter
- end point supports additional filtering with labels and inbox ids
- swagger doc

app/controllers/api/v1/accounts/conversations_controller.rb

@@ -15,6 +15,12 @@ class Api::V1::Accounts::ConversationsController < Api::V1::Accounts::BaseContro
     @conversations_count = result[:count]
   end
 
+  def search
+    result = conversation_finder.perform
+    @conversations = result[:conversations]
+    @conversations_count = result[:count]
+  end
+
   def create
     @conversation = ::Conversation.create!(conversation_params)
   end