Upload "post attachments" in sync-post task

[fennifith]

When a post is synced to hoof, any adjacent files (images, pdfs, powerpoints, and subfolders) should also be uploaded to S3 and tagged with the post slug.

• These should be tracked in a new post_attachments table.
  • Each attachment should have an "attachment_name" (the original file name) and "attachment_key" (the location it's stored at in S3).
  • If the attachment is an image, it should be minimally processed to ensure a max size (see: processProfileImage. The resulting height/width should also be stored in the attachments table.

If the asset is removed from the repo, it should also be deleted from S3.

Likewise, if the post is deleted from the repo, all of its assets should be removed from S3.

[szymonchudy]

Should we support videos as well?

If the asset is removed from the repo, it should also be deleted from S3.

Likewise, if the post is deleted from the repo, all of its assets should be removed from S3.

Side question: Should we also remove MD files? While storage is cheap and MD files are small, if someone deletes something from GitHub, they likely want it removed from the entire system. Additionally, it's always beneficial to avoid bloating the bucket.