SNMP set custom scan_interval

Hi!

I’m pulling port label name from my switch using snmp so I can see the “official” name of my ports. Easier than Port X when you have 28 of them and it avoids me having to edit config file when something changes.

Since the alias/name/labels won’t change that often, I’d like to reduce stress by making the scan interval higher for those OIDs.

- platform: snmp
  name: TPLink Switch Port 1 Label
  host: !secret tplink_switch_ip
  auth_protocol: 'hmac-sha'
  username: !secret tplink_switch_snmp_username
  auth_key: !secret tplink_switch_snmp_authkey
  priv_protocol: 'des'
  priv_key: !secret tplink_switch_snmp_privkey
  version: '3'
  baseoid: 1.3.6.1.2.1.31.1.1.1.18.49153
  update_interval: 900

Some integrations support an update_interval field. I suggest the implementation of such, while ensuring a safe minimum is required (ie: 10 seconds like now, 10<=x).