[BUG] Upgrading to 5.0 beta3 (from beta2) introduced the following error with csharp-netcore generation (net50 not in supported versions)

Command:

openapi-generator-cli generate -i $SWAGGER_FILE -g csharp-netcore -o $output -c $configFile --git-repo-id=$GIT_REPO --git-user-id=$GIT_USER \
--additional-properties=packageVersion=$VERSION,packageName=$packageName

Output:

Exception in thread "main" java.lang.IllegalArgumentException: Invalid .NET framework version: net5.0. List of supported versions: netstandard1.3, netstandard1.4, netstandard1.5, netstandard1.6, netstandard2.0, netstandard2.1, netcoreapp2.0, netcoreapp2.1, netcoreapp3.0, netcoreapp3.1, net47
        at org.openapitools.codegen.languages.CSharpNetCoreClientCodegen.processOpts(CSharpNetCoreClientCodegen.java:579)
        at org.openapitools.codegen.DefaultGenerator.configureGeneratorProperties(DefaultGenerator.java:250)
        at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:862)
        at org.openapitools.codegen.cmd.Generate.execute(Generate.java:432)
        at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
        at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)

Config File:

{
	"targetFramework": "net5.0"
}

Start at CSharpNetCoreClientCodegen.java:579, where processOpts rejects the targetFramework value from the supplied config file. Check how supported .NET framework versions are validated for csharp-netcore generation. Done means the shown command accepts net5.0 and completes generation without the reported exception.