auth lmdb: full support for comments

[Habbie]

Short description

WIP. TODO:

• comment search
• comment sorting? (by timestamp) - but we already group by RRset, so there's not much sorting to be done really
• schema upgrade
• better serialisation (need something stable/canonical; looks like protozero might be it. Alternatively, have my -hash- depend on something simple and stable while the serialisation is at least robust)
• CAP flag?
• squashing
• fix pdnsutil comment add example.com foobar A 'hello protobuf' petre -> Error: std::string keyConv(const T&) [with T = DNSName; typename std::enable_if<std::is_same<T, DNSName>::value, T>::type* <anonymous> = 0; std::string = std::__cxx11::basic_string<char>] Attempt to serialize an unset DNSName

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)
• checked that this code was merged to master

[miodvallat]

Maybe prefer putting a pointer to the *dbi to use here rather than a bool? Might not be as simple as it looks.

[Habbie]

then we'd have to compare dbi pointers in getInternal, because the logic is different for comments vs. records (which I am unhappy about but I haven't found a clean refactor for it yet)

[miodvallat]

I thought this would be part of the rrset commands. As in rrset add-comment, rrset list-comment, rrset forget-comment, rrset why-the-hell-did-I-forget-to-put-a-comment, etc.

[Habbie]

makes perfect sense

[coveralls]

Pull Request Test Coverage Report for Build 19674913787

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 136 of 150 (90.67%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall first build on lmdb-full-comments at 73.078%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
modules/lmdbbackend/lmdbbackend.cc	117	122	95.9%
pdns/dnsbackend.cc	19	28	67.86%

Totals
Change from base Build 19426528573:	73.1%
Covered Lines:	128116
Relevant Lines:	164582

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💛 - Coveralls

[Habbie]

rebased