Add user tripcodes

Users can separate their name and a password with ## to create the
illusion of consistent posting.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

board/utils.py

@@ -1,9 +1,12 @@
-from typing import Optional, TYPE_CHECKING
-from django.utils import timezone
-from django.conf import settings
+import base64
+import hashlib
 import ipaddress
 import random
 import string
+from typing import Optional, TYPE_CHECKING
+
+from django.utils import timezone
+from django.conf import settings
 
 from board.models import Ban, RangeBan
 
@@ -56,3 +59,11 @@ def generate_user_token() -> str:
     User tokens need not be secure so this is a simple implementation.
     """
     return "".join(random.choices(string.ascii_letters, k=settings.USER_TOKEN_LENGTH))
+
+
+def generate_tripcode(value: str) -> str:
+    hasher = hashlib.sha256()
+    hasher.update(settings.TRIPCODE_SALT.encode())
+    hasher.update(value.encode())
+    trip = base64.b64encode(hasher.digest()).decode("ascii")
+    return trip[0:10]