Add service scaffolding

[sagikazarmark]

Easily generate a new service:

mga create|scaffold service internal/mypkg

The package should be created (if not exists) with the following content:

package mypkg

// +kit:endpoint:errorStrategy=service

// Service is [your business service description].
type Service interface {
    // Add your service calls here
}

The command SHOULD NOT overwrite existing files.