issue: track messages in database

issue: track messages in database

Replace file storage by PostgreSQL table, similar to comments in commit
v4.0-21-g0cc6251412 (2019-10-27) [nieuws/replies: read contents from database].

Existing files are imported similar to earlier comments:

	ls melding/2*/*.html | perl -MFile::Slurp -lnE ' #/
		my ($page, $date, $name) = split m{/};
		$name =~ s/(\d+-\d+)-// and $date .= "-$1";
		my $closed = qx(stat -c%y "$page/.tags/opgelost/$date-$name" 2>/dev/null);
		chomp $closed;
		$name =~ s/\.html$//;
		my $html = read_file($_);
		$html =~ s{<h2>(.*?)</h2>\n+}{}; my $title = $1;
		chomp, s/\\\K/\\/g, s/\n/\\n/g, s/\t/\\t/g for $html;
		say join "\t", $page, $date, $name, $title, $html, $closed || "\\N";
	' | psql lijtweg -c 'COPY issues (page, created, link, subject, body, closed) FROM STDIN'

Afterwards, the following queries can be executed to convert and clean up
these imported rows further:

	-- rename issue references to new page ids
	UPDATE comments c SET page = (SELECT coalesce((SELECT page||'/'||id
		FROM issues WHERE c.page LIKE page || '/%-' || link), c.page));

	-- move authorship contents to dedicated column
	SELECT id, regexp_matches(body, '<p class="right">(?:Ingediend door |<em>)?([^<]*)')
		FROM issues WHERE body ~ 'right';
	UPDATE issues SET author = 'cees' WHERE body ~ '<p class="right">.*Cees';
	UPDATE issues SET author = '301' WHERE body ~ '<p class="right">.*de Roos';
	UPDATE issues SET body = regexp_replace(body, E'\n+<p class="right">.*</p>$', '')
		WHERE body ~ 'right';