Generate Kotlin v4 client

[alarvi]

Add the kotlin client for both v2 and v4 apis.

They have been generated with the following commands:

openapi-generator generate -i ./monitoring.yaml -g kotlin -o ./kotlin/monitoring --package-name enlighten.monitoring --http-user-agent EnphaseOpenAPI/kotlin

openapi-generator generate -i ./commissioning.yaml -g kotlin -o ./kotlin/commissioning --package-name enlighten.commissioning --http-user-agent EnphaseOpenAPI/kotlin

openapi-generator generate -i ./enlighten.yaml -g kotlin -o ./kotlin/commissioning --package-name enlighten --http-user-agent EnphaseOpenAPI/kotlin