Add example for custom DNS server with port number

[sed-i]

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What does this PR aim to accomplish?:
A detailed description, screenshots (if necessary), as well as links to any relevant GitHub issues
Provide an example for how to specify a custom DNS address including a port number.

How does this PR accomplish the above?:
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Update a string.

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None.

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[dschaper]

Hi, can you make sure your commits and PR target are the correct branch. The contributors guide has the information.

[sed-i]

Hi, can you make sure your commits and PR target are the correct branch. The contributors guide has the information.

Thanks @dschaper. Done.

[yubiuser]

I vaguely remember we once had an issue where IP#PORT combination during the installation were not accepted. I can't find the issue right now. It might have been resolved already by #4121.

@sed-i Did you try, if a port can be added to the upstream DNS server IP during the installation successfully?

[sed-i]

@sed-i Did you try, if a port can be added to the upstream DNS server IP during the installation successfully?

I think it works:

$ sudo grep -Irn "127\.0\.0\.1#5335" /etc
/etc/pihole/setupVars.conf:4:PIHOLE_DNS_1=127.0.0.1#5335
/etc/pihole/setupVars.conf:5:PIHOLE_DNS_2=127.0.0.1#5335
/etc/dnsmasq.d/01-pihole.conf:38:server=127.0.0.1#5335

However, I do not know at the moment how to test this: pi-hole/docs#695

[yubiuser]

Thanks for testing

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/pi-hole-ftl-v5-16-web-v5-13-and-core-v5-11-1-released/56384/1