Use PostgreSQL unaccent extension und use it for user filters

[oliverguenther]

https://community.openproject.org/work_packages/53371

I first looked at the ICU collations, but they have their own drackbacks, so I went to the unaccent core/contrib extension instead. We're currently not using and indexes on the concatenated user fields anyway, so the impact should not bee to bad. I've tested this on the public community dump for adequate sized user collection prior to filtering.

See also for more information on ICU and different approaches and their drawbacks: https://stackoverflow.com/a/11007216/420614

Assigning to 13.5 due to the added migration

[klaustopher]

Would we need something in our container setup to include postgres-contrib, or is it already available?

[oliverguenther]

Would we need something in our container setup to include postgres-contrib, or is it already available?

we already have other extensions enabled from this package, which is shipped with in most distributions (and docker), but was missing in e.g, RHEL. There it has to be enabled manually, but most installations will have done so already due to older migrations.