contrib/docker: Ensure correct encoding and locale settings on DB creation (#6921)

Signed-off-by: Fridtjof Mund <fridtjof@das-labor.org>

changelog.d/6921.docker

@@ -0,0 +1 @@
+Databases created using the compose file in contrib/docker will now always have correct encoding and locale settings. Contributed by Fridtjof Mund.

contrib/docker/docker-compose.yml

@@ -56,6 +56,9 @@ services:
     environment:
       - POSTGRES_USER=synapse
       - POSTGRES_PASSWORD=changeme
+      # ensure the database gets created correctly
+      # https://github.com/matrix-org/synapse/blob/master/docs/postgres.md#set-up-database
+      - POSTGRES_INITDB_ARGS="--encoding=UTF-8 --lc-collate=C --lc-ctype=C"
     volumes:
       # You may store the database tables in a local folder..
       - ./schemas:/var/lib/postgresql/data