Server ban exemption system (#15076)

Content.Server/Database/ServerDbBase.cs

@@ -332,6 +332,52 @@ namespace Content.Server.Database
 
         public abstract Task AddServerBanAsync(ServerBanDef serverBan);
         public abstract Task AddServerUnbanAsync(ServerUnbanDef serverUnban);
+
+        protected static async Task<ServerBanExemptFlags?> GetBanExemptionCore(DbGuard db, NetUserId? userId)
+        {
+            if (userId == null)
+                return null;
+
+            var exemption = await db.DbContext.BanExemption
+                .SingleOrDefaultAsync(e => e.UserId == userId.Value.UserId);
+
+            return exemption?.Flags;
+        }
+
+        public async Task UpdateBanExemption(NetUserId userId, ServerBanExemptFlags flags)
+        {
+            await using var db = await GetDb();
+
+            if (flags == 0)
+            {
+                // Delete whatever is there.
+                await db.DbContext.BanExemption.Where(u => u.UserId == userId.UserId).ExecuteDeleteAsync();
+                return;
+            }
+
+            var exemption = await db.DbContext.BanExemption.SingleOrDefaultAsync(u => u.UserId == userId.UserId);
+            if (exemption == null)
+            {
+                exemption = new ServerBanExemption
+                {
+                    UserId = userId
+                };
+
+                db.DbContext.BanExemption.Add(exemption);
+            }
+
+            exemption.Flags = flags;
+            await db.DbContext.SaveChangesAsync();
+        }
+
+        public async Task<ServerBanExemptFlags> GetBanExemption(NetUserId userId)
+        {
+            await using var db = await GetDb();
+
+            var flags = await GetBanExemptionCore(db, userId);
+            return flags ?? ServerBanExemptFlags.None;
+        }
+
         #endregion
 
         #region Role Bans
@@ -985,6 +1031,5 @@ namespace Content.Server.Database
 
             public abstract ValueTask DisposeAsync();
         }
-
     }
 }