[SDK] Create the Stats endpoint - Go

[LanaAb]

• [x] Get a list of sent campaigns
• [x] Get stats for a sent campaign
• [x] Get a subscribers of sent campaign
• [x] Get a list of forms by type
• [x] Get a stats of a form by type
• [x] Get subscribers of a form by type
• [x] Get a list of automations
• [x] Get a stats for a specific automation
• [x] Get a list of subscribers of a specific automation by type (completed, failed, etc.)

[robgordon89]

done