[pkg] prepare 3.18.7

[migration/3.18] speed up the migration and be a little bit more informative Closes #4619277.

[schemaserial] be robust against duplicated CWUniqueTogetherConstrain entities arising from bug in the pre 3.18 era Closes #4619278.

[server] Handle unique constraint violations under recent sqlite The error message changed from "columns foo, bar, baz are not unique" to "UNIQUE constraint failed: table.foo, table.bar, table.baz". Closes #3564510

[merge] backport 3.17 fixes

Added tag cubicweb-version-3.17.18, cubicweb-debian-version-3.17.18-1, cubicweb-centos-version-3.17.18-1 for changeset cda4b066933f

[pkg] prepare 3.17.18

[source/native] handle newer Integrity error messages from sqlite > 3.7 Similar to a0cf2993b6d3 that was done for 3.18.

[source/native/backup_restore] have a unique tunable blocksize for the dump phase Thus we make memory errors much less likely. Closes #4618949.

[urlpublishing] handle sub-types in RestPathEvaluator Since commit 31a1813d53f3 "[entity/url publishing] fetch_rqlst should use 'is_instance_of' instead of 'is'", the RestPathEvaluator's input rset can have more than one etype, so it can't always use sameetypelist. Related to #3825488

[views] fix ecsvexport selector introduced by e48e5a597ccc Fix the view and make web/test/test_views.py pass again.

Add custom checker for Password values We override the default converter to pass Binary values through, but don't do anything about the checker. This worked previously because yams allowed StringIO instances, although its converter didn't do the right thing for them. Fixing this in yams requires that we properly register a checker.

[component] give Links a __repr__

[debian] move markdown dependency from cubicweb-web to cubicweb-common Pointed out by David Douard.

[web/auth] stop playing games with locals() We only want to know if any retriever found something.