Explain what REST parameters are for email settings

The documentation does not clearly explain what the parameters mean and what they are used for when setting email configurations. Currently we have the following options and their descriptions (taken from the Web UI).

auto_failover_node - Node was auto-failed-over

auto_failover_maximum_reached - Maximum number of auto-failed-over nodes was reached

auto_failover_other_nodes_down - Node wasn't auto-failed-over as other nodes are down at the same time

auto_failover_cluster_too_small - Node was not auto-failed-over as there are not enough nodes in the cluster running the same service

auto_failover_disabled - Node was not auto-failed-over as auto-failover for one or more services running on the node is disabled

ip - Node's IP address has changed unexpectedly

disk - Disk space used for persistent storage has reached at least 90% of capacity

overhead - Metadata overhead is more than 50%

ep_oom_errors - Bucket memory on a node is entirely used for metadata

ep_item_commit_failed - Writing data to disk for a specific bucket has failed

audit_dropped_events - Writing event to audit log has failed

indexer_ram_max_usage - Approaching full Indexer RAM warning

ep_clock_cas_drift_threshold_exceeded - Remote mutation timestamp exceeded drift threshold