modules/snipe-it: remove PostgreSQL support

Since Laravel, the PHP framework used by Snipe-IT in general supports PostgreSQL
and other database systems, there was a slight hope that it would just work™,
even though Snipe-IT itself officially only supports MySQL.  Turns out it
doesn't.

SQLite seems to work fine so far.

modules/services/snipe-it.nix

@@ -19,8 +19,6 @@ let
       fileinfo
       bcmath
       gd
-    ] ++ optionals usePgsql [
-      pdo_pgsql
     ] ++ optionals useMysql [
       pdo_mysql
     ])
@@ -32,7 +30,6 @@ let
   group = cfg.group;
 
   db = cfg.database;
-  usePgsql = db.type == "pgsql";
   useMysql = db.type == "mysql";
   useSqlite = db.type == "sqlite";
 
@@ -120,8 +117,8 @@ in {
 
     database = {
       type = mkOption {
-        type = types.enum [ "pgsql" "mysql" "sqlite" ];
-        default = "pgsql";
+        type = types.enum [ "mysql" "sqlite" ];
+        default = "mysql";
         description = "Database engine to use.";
       };
       host = mkOption {
@@ -140,7 +137,7 @@ in {
       name = mkOption {
         type = types.str;
         default = "snipe-it";
-        description = "Name of the PostgreSQL or MySQL database.";
+        description = "Name of the MySQL database.";
       };
       username = mkOption {
         type = types.str;
@@ -315,12 +312,6 @@ in {
   };
 
   config = mkIf cfg.enable {
-    assertions = [
-      { assertion = usePgsql -> db.port == 5432;
-        message = "PostgreSQL is currently only supported with default port 5432.";
-      }
-    ];
-
     warnings =
        optional (!useMysql) ''
          Please note: Using another database than MySQL isn't officially supported.
@@ -328,15 +319,6 @@ in {
 
     environment.systemPackages = [ artisan ];
 
-    services.postgresql = mkIf (usePgsql && db.host == "localhost") {
-      enable = mkDefault true;
-      ensureDatabases = [ db.name ];
-      ensureUsers = [{
-        name = db.username;
-        ensurePermissions = { "DATABASE \"${db.name}\"" = "ALL PRIVILEGES"; };
-      }];
-    };
-
     services.mysql = mkIf (useMysql && db.host == "localhost") {
       enable = mkDefault true;
       package = mkDefault pkgs.mariadb;
@@ -431,8 +413,7 @@ in {
     systemd.services.snipe-it-setup = {
       description = "Preparation tasks for Snipe-IT";
       before = [ "phpfpm-snipe-it.service" ];
-      after = optional useMysql "mysql.service"
-        ++ optional usePgsql "postgresql.service";
+      after = optional useMysql "mysql.service";
       wantedBy = [ "multi-user.target" ];
       serviceConfig = {
         Type = "oneshot";