Changes to list avatars

added the non-success response with the status 503

added the optional property data/items/sourceImageUrl to the response with the 200 status

the response property data/items/activeVersion became nullable for the status 200

added the new optional query request parameter renderStyle

added the new optional query request parameter tags

added the non-success response with the status 403

added the optional property data/items/description to the response with the 200 status

added the optional property data/items/displayTags to the response with the 200 status

added the optional property data/items/idleVideoUrl to the response with the 200 status

added the optional property data/items/landscapeImageUrl to the response with the 200 status

added the optional property data/items/portraitImageUrl to the response with the 200 status

added the optional property data/items/renderStyle to the response with the 200 status