Add user specific quotas

user_without_quotas will overwrite mem_limit/cpu_limit. Users in this
list will have unlimited RAM and CPU.

special_user_quotas will overwrite mem_limit and cpu_limit for a
specific user. It is possible to set mem_limit OR/AND cpu_limit.

user_without_quotas is stronger than special_user_quotas.

systemdspawner/systemdspawner.py

@@ -3,7 +3,7 @@
 import time
 import subprocess
 import shlex
-from traitlets import Bool, Int, Unicode, List
+from traitlets import Bool, Int, Unicode, List, Dict
 from tornado import gen
 
 from jupyterhub.spawner import Spawner
@@ -70,6 +70,21 @@ class SystemdSpawner(Spawner):
         """
     ).tag(config=True)
 
+    users_without_quotas = List(
+        None,
+        allow_none=True,
+        help='''
+            List of users that will have unlimited mem_limit and cpu_limit, it will overwrite special_user_quotas even if
+            it's set for the user.
+        '''
+    ).tag(config=True)
+
+    special_user_quotas = Dict(
+        None,
+        allow_none=True,
+        help='Dict with users as key and cpu_limit/mem_limit as value. It will overwrite mem_limit/cpu_limit.'
+    ).tag(config=True)
+
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         # All traitlets configurables are configured by now
@@ -83,7 +98,6 @@ def __init__(self, *args, **kwargs):
 
         self.log.debug('user:%s Initialized spawner with unit %s', self.user.name, self.unit_name)
 
-
     def _expand_user_vars(self, string):
         """
         Expand user related variables in a given string
@@ -180,6 +194,17 @@ def start(self):
 
         cmd.append('--setenv=SHELL={shell}'.format(shell=self.default_shell))
 
+        if self.users_without_quotas and self.user.name in self.users_without_quotas:
+            # If users_without_quotas is set for the user, it will overwrite mem_limit and cpu_limit
+            self.mem_limit = None
+            self.cpu_limit = None
+        elif self.special_user_quotas and self.user.name in self.special_user_quotas:
+            # If the user has a specific value for mem_limit or cpu_limit, it will overwrite the default value
+            if 'mem_limit' in self.special_user_quotas[self.user.name]:
+                self.mem_limit = self.special_user_quotas[self.user.name]['mem_limit']
+            if 'cpu_limit' in self.special_user_quotas[self.user.name]:
+                self.cpu_limit = self.special_user_quotas[self.user.name]['cpu_limit']
+
         if self.mem_limit is not None:
             # FIXME: Detect & use proper properties for v1 vs v2 cgroups
             cmd.extend([