Generate build plugin sources for JSON schema generator

[andriy-dmytruk]

Switch JSON schema to generate Maven and Gradle configurations based on micronaut-build-plugin-sourcegen.

The generated plugins will:

• Have the same properties defined
• Have the javadoc copied as defined in this repo
• Add the generated files as build sources

This would simplify support, as additional properties would require no manual changes in the plugins. Some properties would already be added in this PR: #163.

Current support

Maven	Gradle	Plugingen
inputURL	inputUrl	inputURL
inputFile	inputFile	inputFile
inputDirectory	inputDirectory	inputDirectory
language default=JAVA	lang default=JAVA	language default=JAVA
outputDirectory default="${project.build.directory}/generated-sources/jsonschema"	outputDirectory	outputDirectory
outputPackageName default=io.micronaut.jsonschema	outputPackageName	outputPackageName default=io.micronaut.jsonschema
outputFileName	outputFileName	outputFileName
acceptedUrlPatterns	acceptedUrlPatterns	acceptedUrlPatterns
enabled default=false	enabed default=true	enabled default=false/true

[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 70%)

See analysis details on SonarQube Cloud

[elifKurtay]

I am a bit confused by the outputDirectory here.
In the previous version, it was not required and its default value was generated/jsonschema. It is also not used in the guide examples and docs etc. And we added the language source directories after the given outputDirectory in the plugins. So the final address used to be: outputDirectory + languageDir + outputPackageName + outputFileName.
But here, we are setting the outputDirectory as the languageDir. Is this what is desired?

[andriy-dmytruk]

Yes, I added the different language folders, so that is more explicit where the files are generated.

The folders have to be added to the classpath in different ways (like groovy to the groovy source sets if groovy plugin exists).

This is a change from the previous behavior when output directory was overridden, but also means that the directory is added to the appropriate classpath.