Add cpp-oatpp-server generator (alpha)

[wing328]

To build the new generator cpp-oatpp-server:
(ref: https://github.com/oatpp/oatpp)

git clone https://github.com/OpenAPITools/openapi-generator/
cd openapi-generator
git checkout cpp-oatpp-server-generator

Linux: ./mvnw clean package -DskipTests
Windows: .\mvnw.bat clean package -DskipTests

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g cpp-oatpp-server -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml -t modules/openapi-generator/src/main/resources/cpp-oatpp-server -o /var/tmp/cpp-oatpp-server

The new generator is created based on cpp-pistache-server. To start with, we'll need to update the mustache templates to use oatpp. Templates can be found in modules/openapi-generator/src/main/resources/cpp-oatpp-server

PR checklist

• 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.
• If contributing template-only or documentation-only changes which will change sample output, build the project beforehand.
• Run the shell script ./bin/generate-samples.shto update all Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master
• Copy the technical committee to review the pull request if your PR is targeting a particular programming language.

[Crisliu7]

Hi William, thanks for your effort to create this. May I ask is this generator stable to use? Any plan to merge it to master branch or release it?

[wing328]

@Crisliu7 I've not seen any contributions to this generator so far. Would you have time to contribute to this PR to make the output works (at least with basic APIs like petstore that we use for testing in this project)?

[makru86]

I plan to work on it, to create cpp-oatpp-server generator. But I will start from scratch, new.sh -n cpp-oatpp -s -t. Will post updates in this thread.

https://github.com/atokama/openapi-generator

[makru86]

preparing hand-written oatpp-petstore-server https://github.com/atokama/oatpp-petstore-server

i plan to use async endpoints, to enable non-blocking IO in handlers. https://oatpp.io/docs/oatpp-coroutines/

[makru86]

continue work here https://github.com/makru86/oatpp-petstore

[makru86]

I manually created Petstore API with C++ and Oat++.

Anyone welcome to use it as a reference for a cpp-oatpp-server generator.

https://github.com/makru86/oatpp-petstore-starter
Ref ticket @oatpp repo: oatpp/oatpp#331