the current transaction model only rollsback on db failures. this
changeset makes the transaction encapsulate the entire NewPull flow. if
creating the pds record fails, the db is still rolled back.

Also does some driveby config refactoring.

Add a space between the Discord link and the next word "or". This only
shows up on the timeline if you are not logged in...meaning it's one of
the first things a new user sees.

gotta be more explicit apparently

subsequently, every RenderMarkdown call has been wrapped with
bluemonday sanitization.