nixos/postgresql: fix merging of shared_preload_libraries option

Closes #386804

The issue with coercing to `types.str` is that it's not mergeable, so
any declarations will result in an eval error like this:

    error: The option `interactive.nodes.tmp.services.postgresql.settings.shared_preload_libraries' has conflicting definition values:
    - In `/home/ma27/Projects/nixpkgs-hack/tmp.nix@node-tmp': "foo"
    - In `/home/ma27/Projects/nixpkgs-hack/tmp.nix@node-tmp': "bar2"
    Use `lib.mkForce value` or `lib.mkDefault value` to change the priority on any of these definitions.

Using a mergeable type (`types.comma`, i.e. a string, where all declarations
get joined with a comma as delimiter) fixes the problem.

0 files changed, 0 insertions, 0 deletions