This commit adds a `useUnless` helper method which can be used as a middleware for express.
It receives an express-middleware and an array of paths.
When a request matches one of the given paths, this middleware does nothing.
Otherwise the given middleware is called.
For the express-session middleware this helper middleware is used to avoid session creation on purely status routes.
See #1446
Signed-off-by: Erik Michelson <github@erik.michelson.eu>
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