What's changed?

This PR adds database account expiry monitoring for MySQL as part of issue #2757.

A new account_expiry metric is introduced in app-mysql.yml that exposes:

• user
• host
• password_lifetime
• password_last_changed
• password_expired
• days_left (remaining days before expiry)

This enables HertzBeat users to alert on:

• expired accounts
• accounts expiring in N days
• security & credential risks

Verification

I validated this using real MySQL users:

SELECT
  user,
  host,
  password_lifetime,
  password_last_changed,
  password_expired,
  IF(password_lifetime IS NULL,
     NULL,
     password_lifetime - DATEDIFF(NOW(), password_last_changed)
  ) AS days_left
FROM mysql.user;

Test users:

test_expire_5 → 4 days remaining
test_expired → expired

HertzBeat UI shows the same values for Days Left and Expired flag.

Screenshots attached:

Checklist

• I have read the Contributing Guide
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.

Add or update API

• I have added the necessary e2e tests and all cases have passed.