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/accounts/search_controller_spec.rb

@@ -112,6 +112,7 @@ RSpec.describe 'Search', type: :request do
 
         expect(response_data[:payload].keys).to contain_exactly(:messages)
         expect(response_data[:payload][:messages].length).to eq 2
+        expect(response_data[:payload][:messages].first[:message_type]).to eq 0
       end
     end
   end