fix: message_type inconsistency across message end points (#10108)

The `before_type_cast` method sometimes returns a string for
`message_type`, creating inconsistencies in different payloads. This
pull request will remove all `before_type_cast` usage and replace it
with `to_i` methods.

spec/controllers/api/v1/widget/messages_controller_spec.rb

@@ -54,6 +54,7 @@ RSpec.describe '/api/v1/widget/messages', type: :request do
         expect(response).to have_http_status(:success)
         json_response = response.parsed_body
         expect(json_response['content']).to eq(message_params[:content])
+        expect(json_response['message_type']).to eq 0
       end
 
       it 'does not create the message' do