Updates the dns_opnsense.sh Bourne shell script for OPNSense v25.7 series:
1. Fixes historical error in rm_record() [used incorrect response variable]
2. Improves debug messaging in rm_record()
3. Fixes _get_root() for change in OPNsense API
* Response is now split into pseudo-rows
* We now iterate through pseudo-rows for matching domainname field
4. Fixes _existingchallenge() for change in OPNsense API
* Fixes unreliable regex for uuid
* Adds domain regex and %domain field
5. Fixes historical error in _existingchallenge() [incorrect variable syntax]
Resolves#6467
Signed-off-by: benyamin-codez <115509179+benyamin-codez@users.noreply.github.com>
