Add Micronaut server generator

[andriy-dmytruk]

Description

Adds server implementation using Micronaut framework.

Changes to folder structure in the modules/open-api-generator/src/main/resources/java-micronaut folder in order to retain some common client and server features and splitting others - (common, client, server) folders.

Tasks

• Added generator class
• Registered class in SPI file modules/openapi-generator/src/main/resources/META-INF/services/org.openapitools.codegen.CodegenConfig, verified that build does not fail ./mvnw clean package
• Added test class in modules/openapi-generator/src/test
• Created config ./bin/configs/java-micronaut-server.yaml
• Generated samples with ./bin/generate-samples.sh, verified that all test pass with ./mvnw package integration-test -P "java-micronaut-client,java-micronaut-server,-openapi-generator
• Generated docs ./bin/utils/export_docs_generators.sh

Mentions

• Openapi generator core team member @wing328
• Micronaut creator @graemerocher
• Openapi generator Java Technical committee: @bbdouglas @sreeshas @jfiala @lukoyanov @cbornet @jeff9finger @karismann @Zomzog @lwlee2608 @nmuesch

[nyilmaz]

@andriy-dmytruk tested with this pr, found 2 issues,

1. in those files:

params/beanValidation.mustache
model/beanValidation.mustache

@Email annotation should be proceeded with a single space, otherwise code is generated like;

@EmailString

2. controller.mustache has unused import:

import io.micronaut.http.client.annotation.Client;

[andriy-dmytruk]

@nyilmaz Thanks for the info. I will make corrections accordingly.

[pbthorste]

This is a very interesting PR - what is needed to get it merged ?

[wing328]

Tested locally and the result is good.