v1.6.1 - Announcement endpoint - add carousel support

[mjstealey]

Support Carousel as part of announcements endpoint

• [x] add new announcement_type option - carousel as string
• [x] add new data attribute background_image_url as string
• [x] add new data attribute sequence as integer
• [x] add logic for carousel object type
  • sequence is integer between 1 and MAX_ACTIVE_CAROUSEL_ITEMS
  • auto-increment if sequence number requested is already taken (until an open number is found)

Data object - when announcement_type = carousel:

{
  "announcement_type": "carousel",  <-- required, options: [ "carousel", "facility", "maintenance", "news" ]
  "background_image_url": "string", <-- new field - URL to image (optional)
  "button": "string",               <-- (required)
  "content": "string",              <-- (required)
  "sequence": number,               <-- (required)
  "is_active": true,                <-- (required)
  "link": "string",                 <-- (required)
  "title": "string"                 <-- (required)
}

[mjstealey]

merged, closing