fix: more flexible polymorphic types lookup

[bf4]

• fix: more flexible polymorphic types lookup. replaces https://github.com/cerebris/jsonapi-resources/pull/1424

• test: add polymorphic lookup tests

  they pass on v-11-dev

  I'm going to look into the existing lookup warnings

  now

  [POLYMORPHIC TYPE NOT FOUND] No polymorphic types found for fileable
  [POLYMORPHIC TYPE] No polymorphic types found for FilePropertiesResource
  fileable
  [POLYMORPHIC TYPE NOT FOUND] No polymorphic types found for respondent
  [POLYMORPHIC TYPE] No polymorphic types found for QuestionResource
  respondent
  [POLYMORPHIC TYPE NOT FOUND] No polymorphic types found for respondent
  [POLYMORPHIC TYPE] No polymorphic types found for AnswerResource respondent
  [POLYMORPHIC TYPE NOT FOUND] No polymorphic types found for keepable
  [POLYMORPHIC TYPE] No polymorphic types found for KeeperResource keepable

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