SVCB: allow parsing keys in generic format without value

[zeha]

Short description

To avoid other issues, increase strictness of value checks for known keys, regardless if they are in generic or canonical format.

Also add a test for key00NNN (= leading zeroes).

#15479

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master

[coveralls]

Pull Request Test Coverage Report for Build 15293710190

Details

• 73 of 75 (97.33%) changed or added relevant lines in 3 files are covered.
• 52 unchanged lines in 15 files lost coverage.
• Overall coverage increased (+0.005%) to 63.701%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pdns/rcpgenerator.cc	28	30	93.33%

Files with Coverage Reduction	New Missed Lines	%
ext/json11/json11.cpp	1	64.68%
pdns/validate.cc	1	68.24%
modules/lmdbbackend/lmdbbackend.cc	2	74.66%
pdns/rcpgenerator.cc	2	91.01%
pdns/recursordist/sortlist.cc	2	74.12%
pdns/recursordist/syncres.cc	2	80.26%
pdns/sstuff.hh	2	57.5%
pdns/dnsdistdist/dnsdist-carbon.cc	3	61.8%
pdns/packethandler.cc	3	72.82%
pdns/recursordist/rec-main.cc	3	62.14%

Totals
Change from base Build 15271100803:	0.005%
Covered Lines:	130711
Relevant Lines:	170330

---

💛 - Coveralls

[miodvallat]

LGTM

[zeha]

There's still a parsing issue that I need to debug.

[zeha]

There's still a parsing issue that I need to debug.

Pushed some additional test cases and a fix for that.

[zeha]

@miodvallat could you rereview?

[miodvallat]

Still looking good.