feat: Update API for contact avatar (#4719)

Added the ability to update the contact's avatar via API and Dashboard.

- Contact create and update APIs can now accept avatar attachment parameters [form data].
- Contact create and update endpoints can now accept the avatar_url parameter.[json]
- API endpoint to remove a contact avatar.
- Updated Contact create/edit UI components with avatar support

Fixes: #3428

config/routes.rb

@@ -95,6 +95,7 @@ Rails.application.routes.draw do
             member do
               get :contactable_inboxes
               post :destroy_custom_attributes
+              delete :avatar
             end
             scope module: :contacts do
               resources :conversations, only: [:index]