Rate limit invite endpoint

To prevent hammering on the invite endpoint we throttle requests to the endpoint to 100/day per ip.

Resolves: GREG-84

gregsite/settings/base.py

@@ -268,6 +268,17 @@ INTERNAL_RK_PREFIX = "no.{instance}.greg".format(instance=INSTANCE_NAME)
 
 FEIDE_SOURCE = "feide"
 
+# Rate limit settings of invite endpoint
+REST_FRAMEWORK = {
+    "DEFAULT_THROTTLE_CLASSES": [
+        "rest_framework.throttling.AnonRateThrottle",
+    ],
+    "DEFAULT_THROTTLE_RATES": {
+        "anon": "100/day",
+    },
+}
+
+
 # Used by the OU import from orgreg to distinguish the OuIdentifiers from others
 ORGREG_SOURCE = "orgreg"
 ORGREG_NAME = "orgreg_id"