Nest API entity directories in `api`

[slifty]

Right now the /src/* layer directories in the api package seem to be a blend of "defining the MVC for a specific an entity-api path" and "defining something else related to the api overall"

I believe these are endpoint / entity related directories:

• account
• admin
• archive
• directive
• email
• event
• feature_flag
• folder
• health
• idpuser
• legacy_content
• promo
• record
• share
• share_link
• tag

And these are the "other" directories

• common
• middleware
• routes
• types
• validators

I'd propose it would be great to have the endpoint directories inside of a folder to help improve the legibility of the "src root". Maybe this could be src/entities