home: create 'modules/home' folder

Consolidating all modules under the same path, to clear out the
top-level directory.

modules/home/direnv/lib/postgres.sh

@@ -0,0 +1,22 @@
+#shellcheck shell=bash
+
+layout_postgres() {
+    if ! has postgres || ! has initdb; then
+        # shellcheck disable=2016
+        log_error 'layout_postgres: `postgres` and `initdb` are not in PATH'
+        return 1
+    fi
+
+    # shellcheck disable=2155
+    export PGDATA="$(direnv_layout_dir)/postgres"
+    export PGHOST="$PGDATA"
+
+    if [[ ! -d "$PGDATA" ]]; then
+        initdb
+        cat >> "$PGDATA/postgresql.conf" << EOF
+listen_addresses = ''
+unix_socket_directories = '$PGHOST'
+EOF
+        echo "CREATE DATABASE $USER;" | postgres --single -E postgres
+    fi
+}