The long-awaited ddclient v4 is around the corner.

This task tracks the migration of Dynamic DNS service to use ddclient v4.

ddclient 4.0 brings quite a few changes. Significant ones in the context of VyOS are:

• SSL (TLS) for http(s) conections is enabled by default, we don't need to sent it explicitly anymore
• Protocols like googledomains and woima have been removed since those services are defunct
• checkip.dyndns.org (historically the most common host to detect IP address over webv4/webv6 finally supports tls)
• A few protocols gained dual-stack support (viz., domeneshop, gandi, godaddy, mythicdyn, noip, nsupdate, regfishde, luadns)
• Support for a few new protocols have been added (viz., ddns.fm, he.net, inwx, porkbun)
• Internally, few protocols have modifications (e.g., gandi supports personal access token only)
• Quite a few additional changes and modification have been applied to remove legacy cruft that are internal to the implementation and aren't user facing.

See: https://github.com/ddclient/ddclient/blob/main/ChangeLog.md#2025-01-19-v400 for upstream changelog.

Notes:

1. We used googedomains as default to detect IP address over webv4/webv6 in the past. Since googedomains is not available anymore, we need a migration script to adjust the legacy configuration.
2. We moved from GitHub to Debian Salsa in the past to pull in ddclient source. However, Debian Salsa doesn't catch up with GitHub releases within reasonable timeframe. We are still going to use Debian Salsa as our source (because it has all the necessary Debian packaging toolchain setup), but use a non-tagged (but stable) commit id to pull in the sources in combination with the necessary pactches for the build.