This commit introduces helper functions to easily convert `Injectable`s with
functions compatible with `Route` guards to the corresponding guard functions.
These functions will serve to aid in migrating off of the now deprecated
class-based guards, but also provide an easy avenue to still defining
guards as `Injectable` classes if that is desired.
PR Close#48709
This commit updates the docs of the functional guards and resolvers to improve the migration
experience when moving away from class-based equivalents.
PR Close#48873
Andrew Scott