Package warmup allows to register hooks executed during the server warmup.
All registered hooks should be optional. Warmup can be skipped.
InstallHandlers installs HTTP handlers for warmup /_ah/* routes.
Register adds a callback called during warmup.
Warmup executes all registered warmup callbacks, sequentially.
Doesn't abort on individual callback errors, just collects and returns them all.
Callback will be called during warmup.