Added postgres support (#556)

Content.Server.Database/PrefsDb.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using Microsoft.EntityFrameworkCore;
 
@@ -7,12 +8,15 @@ namespace Content.Server.Database
     {
         private readonly PreferencesDbContext _prefsCtx;
 
-        public PrefsDb(string dbPath)
+        public PrefsDb(IDatabaseConfiguration dbConfig)
         {
-            var optionsBuilder = new DbContextOptionsBuilder<PreferencesDbContext>();
-            optionsBuilder.UseSqlite($"Data Source={dbPath}");
-
-            _prefsCtx = new PreferencesDbContext(optionsBuilder.Options);
+            _prefsCtx = dbConfig switch
+            {
+                SqliteConfiguration sqlite => (PreferencesDbContext) new SqlitePreferencesDbContext(
+                    sqlite.Options),
+                PostgresConfiguration postgres => new PostgresPreferencesDbContext(postgres.Options),
+                _ => throw new NotImplementedException()
+            };
             _prefsCtx.Database.Migrate();
         }