refactor: flatten Contentful asset data structure to match GraphQL API schema

[axe312ger]

This simplifies the asset data structure to match Contentfuls GraphQL API schema.

https://www.contentful.com/developers/docs/references/graphql/#/reference/schema-generation/assets

old schema

type ContentfulAsset implements ContentfulInternalReference & Node @dontInfer {
  file: ContentfulAssetFile
  title: String
  description: String
  sys: ContentfulInternalSys
}

type ContentfulAssetFile {
  url: String
  details: ContentfulAssetFileDetails
  fileName: String
  contentType: String
}

type ContentfulAssetFileDetails {
  size: Int
  image: ContentfulAssetFileDetailsImage
}

type ContentfulAssetFileDetailsImage {
  width: Int
  height: Int
}

new schema

type ContentfulAsset implements ContentfulInternalReference & Node @dontInfer {
  sys: ContentfulInternalSys
  title: String
  description: String
  contentType: String
  fileName: String
  url: String
  size: Int
  width: Int
  height: Int
}