add resource - Item
revise anchor
revise link
Update item.md
revise wording
add resource - attachment
rename file
revise wording
fix wording and url
move url param to query string
Update README.md
remove item_key param as client can check attachments of an item by show an item resource
add remark to indicate that attachment name should be unique
modify item attachment resources to have multiple items attached
move remark to description
add description to item attachment attach resource
revise wording
revise item attachment to attach to only 1 item
Update item.md
Update item_format.md