The default implementation has a safe race, and does not allow for action description addition at runtime.
It can be replaced with an implementation that can reload.
Consumers of the new service that do extra caching are now responsible to look at the version and change the implementation.
Treat actions with a dynamic constraint or httpmethod constraint as
'better' than those with just route constraints.
This is the first criteria used to filter down the 'best' match, so it's
applied before parameter-arity.
Yishai Galatzer
Ryan Nowak
Andrew Peters
Pranav K