auth: minor Lua2 backend improvements

[miodvallat]

Short description

There was a new Lua moon two days ago! Let's celebrate with a PR!

This is a followup to #17731 (comment). It is sometimes possible to have a somewhat correct value of the unparseable data (although, if you put false in your script to get the bool case, the reported value will be "0"...), so add it to the exception text.

While there, fix a documentation error and add a faster lookupEnd implementation.

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document, including the AI Policy, and added a "Signed-off-by" to my commits
• 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)

[coveralls]

Coverage Report for CI Build 29501794908

Coverage increased (+0.3%) to 71.132%

Details

• Coverage increased (+0.3%) from the base build.
• Patch coverage: 18 uncovered changes across 1 file (11 of 29 lines covered, 37.93%).
• 35 coverage regressions across 13 files.

Uncovered Changes

File	Changed	Covered	%
modules/lua2backend/lua2api2.cc	29	11	37.93%

Coverage Regressions

35 previously-covered lines in 13 files lost coverage.

Top 10 Files by Coverage Loss	Lines Losing Coverage	Coverage
pdns/dnsdistdist/dnsdist-tcp.cc	4	74.49%
pdns/iputils.hh	4	76.22%
pdns/recursordist/syncres.cc	4	81.23%
modules/lua2backend/lua2api2.cc	3	47.16%
pdns/misc.cc	3	62.05%
pdns/recursordist/recpacketcache.hh	3	91.14%
pdns/remote_logger.cc	3	57.48%
pdns/dnsdistdist/dnsdist-async.cc	2	77.04%
pdns/rcpgenerator.cc	2	89.14%
pdns/recursordist/aggressive_nsec.cc	2	66.2%

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Coverage Stats

Relevant Lines:	172020
Covered Lines:	134131
Line Coverage:	77.97%
Relevant Branches:	82274
Covered Branches:	46754
Branch Coverage:	56.83%
Branches in Coverage %:	Yes
Coverage Strength:	6538011.39 hits per line

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💛 - Coveralls