etherpad: Allow configuring users

etherpad/defaults/main.yml

@@ -14,4 +14,8 @@ etherpads: []
 #     apikey: {{…}}
 #     edit_only: false
 #     require_auth: false
+#     users:
+#       admin:
+#         password: hunter2
+#         is_admin: true
 #

etherpad/templates/settings.json.j2

@@ -107,6 +107,8 @@
     "percentageToScrollWhenUserPressesArrowUp": 0
   },
 
+  "users": {{item.users|default({})|to_json}},
+
   "loadTest": false,
 
   "importExportRateLimiting": {