Complete system.

src/snek/service/user.py

@@ -0,0 +1,16 @@
+from snek.system.service import BaseService 
+from snek.system import security 
+
+class UserService:
+    mapper_name = "user"
+
+    async def create_user(self, username, password):
+        if await self.exists(username=username):
+            raise Exception("User already exists.")
+        model = await self.new()
+        model.username = username
+        model.password = await security.hash(password)
+        if await self.save(model):
+            return model 
+        raise Exception(f"Failed to create user: {model.errors}.")
+