Add thread pool metrics for Webhooks to the health check / status endpoint

[robotdan]

Add Webhook metrics to the health check / status endpoint

Description

Add some additional metrics to the health check / status endpoint for webhooks.

Such as :

• Number of threads available in the executor pool
• Number of threads in-use in the executor pool
• Number of events waiting to be queued by the executor pool
• Number of events that have failed to be added to the queue and will not be sent

This would allow us to see how many failures have occurred, or how many threads are in-use and provide some metrics around the health of FusionAuth as it relates to successfully delivering web hooks.

Related

• Queue for faulty webhooks #391

Community guidelines

All issues filed in this repository must abide by the FusionAuth community guidelines.

[robotdan]

This is available in current versions of FusionAuth.
See event.executor.* metrics in the /api/status endpoint.