Collation

Hey guys,

I'm trying to adopt an application to use PostgresQL. Its a ruby on rails
app and with ActiveRecord, the transition is mostly straight forward. There
is one issue though where I got stuck, perhaps you can help:

One aspect of the app is to store international items. For example a table
"people" might contain "Albrecht Dürer" and "Paul Cézanne" in the same
column. Now, with MySQL, all of the following have at least one result:

SELECT * FROM people WHERE name LIKE '%albrecht%';
SELECT * FROM people WHERE name LIKE '%Anne%';
SELECT * FROM people WHERE name LIKE '%durer%';
SELECT * FROM people WHERE name LIKE '%DÜRER%';
SELECT * FROM people WHERE name LIKE '%cezanne%';
SELECT * FROM people WHERE name LIKE '%Álbrecht%';

I owe that to the collation utf8_general_ci which seems to reasonably fold
a wide range of characters.

For PostrgesQL, I'm using the official docker container:
https://hub.docker.com/_/postgres/

and I tried to use the provided hook to essentially run the following bash
commands:
echo "en_US.UTF-8 UTF-8" >> /etc/locale.gen
echo "de_DE.UTF-8 UTF-8" >> /etc/locale.gen
locale-gen

AFTER the cluster is created. So I understand that initdb uses en_US.UTF-8
for a locale. I also went ahead and:
CREATE COLLATION german (LOCALE = 'de_DE.utf8');

My problem is that I don't (even) get the german collation to work, the
following query yields 'f':

SELECT 'a' COLLATE "german" LIKE 'ä' COLLATE "german";

Shouldn't that be working? Also, the way I understand the docs, there is
not really a way to collate with multiple locales on the same field? This
would mean that there is no equivalent of utf8_general_ci in PostgresQL?

I hope I'm clear and thanks for any help!
Moritz