Fix enum generation for php-symfony generator (!14105) · Merge requests · OpenAPI Tools / openapi-generator

Created by: renaud-twd

@jebentier (2017/07), @dkarlovi (2017/07), @mandrean (2017/08), @jfastnacht (2017/09), @ybelenko (2018/07), @renepardon (2018/12)

Currently, the model generic template is used to generate all DTO classes including enums. This results in empty classes for enums.

This PR just make use of the existing model enum template to generate enum DTOs.

Read the contribution guidelines.
Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
Run the following to build the project and update samples:
```
./mvnw clean package 
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh
```
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