fix: populate ldns submodule and add autotools to LDNS build stage

- Re-cloned zonemaster-ldns with --recurse-submodules so the bundled
  ldns C library source (including Changelog and configure.ac) is present
- Added autoconf, automake, libtool to Dockerfile.backend ldns-build stage
  so libtoolize + autoreconf can generate ldns/configure during make

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

zonemaster-ldns/ldns/examples/ldns-gen-zone.1

@@ -0,0 +1,98 @@
+.TH ldns-gen-zone 1 "10 June 2010"
+.SH NAME
+ldns-gen-zone \- read a zonefile and print it while adding DS records and extra RR's
+.SH SYNOPSIS
+.B ldns-gen-zone 
+.IR ZONEFILE 
+
+.SH DESCRIPTION
+
+\fBldns-gen-zone\fR reads a DNS zone file and prints it. 
+
+It is build for speed, not for a nice formatting. The output
+has one resource record per line and no pretty-printing makeup.
+
+DNSSEC data (NSEC, NSEC3, RRSIG or DNSKEY) is not stripped. You may want to
+use \fBldns-read-zone\fR for that. Existing DS records are also not stripped.
+
+The idea is to use this tool for quickly generating a representative
+artificial zonefile from a real zonefile, to use it for testing purposes.
+
+.SH OPTIONS
+.TP
+\fB-a NUM\fR
+Adds NUM extra artificial NS RRSets to the output. 
+The RRSets owner names start
+with 'xn--' in an attempt to ensure uniqueness (nl.-zone does not support
+IDN's - and this tool was written with that knowledge in mind).
+
+An artificial NS RRSet has two NS records; ns1.example.com and
+ns2.example.com.
+
+.TP
+\fB-p NUM\fR
+Add NUM% of DS RRSets to the NS RRSets (anywhere between
+1-4 DS records per RRSet).
+
+.TP
+\fB-o ORIGIN\fR
+Sets an $ORIGIN, which can be handy if the one in the zonefile
+is set to '@' for example. If there is an $ORIGIN in the zonefile,
+this option will silently be ignored.
+
+.TP
+\fB-s\fR
+This is the recommended way of processing large zones that
+are already sorted and canonicalized (ie lowercase). It skips the
+sorting and canonicalization step that is required for properly
+grouping RRSets together (before adding any DS records to them. Skipping
+this step will speed things up.
+
+It is not recommended to use this option if you want to add DS records
+to unsorted, non-canonicalized zones.
+
+.TP
+\fB-h\fR
+Show usage and exit.
+
+.TP
+\fB-v\fR
+Show version and exit.
+
+.SH EXAMPLES
+
+.TP
+\fBldns-gen-zone \-a 100000 \-p 10 \-s ./zonefile.txt\fR
+Read a zonefile, add 100.000 artificial NS RRSets and 10% of DS records,
+print it to standard output. Don't sort (will only work well if the input
+zonefile is already sorted and canonicalized).
+
+.TP
+\fBldns-gen-zone \-p 10 \-s \-o nl zonefile.txt | named-compilezone \-s relative \-i none \-o zonefile_10.txt nl /dev/stdin\fR
+This creates a nicely formatted zone file with the help of \fBnamed-compilezone\fR.
+It adds 10% DS records to the .nl zone, reformats it and saves it as \fBzonefile_10.txt\fR.
+
+.SH AUTHOR
+Initially written by Marco Davids, several modifications added by Miek
+Gieben, both from SIDN.
+
+.SH REPORTING BUGS
+Report bugs to <dns-team@nlnetlabs.nl>.
+
+.SH BUGS
+Only undiscovered ones.
+
+.SH CAVEATS
+May require a machine with a considerable amount of memory for large zone files.
+
+Fake DS records hashes are generated as digest type SHA-256 (RFC4509). Be aware not to change
+the DIGESTTYPE #define in the source code in anything else but 2 if you want
+to keep things realistic.
+
+Despite a number of efforts, this program is still not the fastest in the
+world.
+
+.SH COPYRIGHT
+Copyright (C) 2010 SIDN. This is free software. There is NO
+warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
+PURPOSE.