Add email max batch and throttle setup

Finetune Django mailer setup by adding email max batch
and throttle settings with default values.

Refs #PV-872

project/settings.py

@@ -72,6 +72,8 @@
     THIRD_PARTY_PARKING_PROVIDER_EMAILS=(list, []),
     MAILER_USE_FILE_LOCK=(bool, False),
     MAILER_LOCK_PATH=(str, "/tmp"),
+    MAILER_EMAIL_MAX_BATCH=(int, 200),
+    MAILER_EMAIL_THROTTLE=(int, 1),
     FIELD_ENCRYPTION_KEYS=(str, ""),
     SENTRY_DSN=(str, ""),
     SENTRY_ENVIRONMENT=(str, ""),
@@ -310,6 +312,8 @@
 EMAIL_BACKEND = "mailer.backend.DbBackend"
 MAILER_USE_FILE_LOCK = env("MAILER_USE_FILE_LOCK")
 MAILER_LOCK_PATH = env("MAILER_LOCK_PATH")
+MAILER_EMAIL_MAX_BATCH = env("MAILER_EMAIL_MAX_BATCH")
+MAILER_EMAIL_THROTTLE = env("MAILER_EMAIL_THROTTLE")
 
 sentry_sdk.init(
     dsn=env.str("SENTRY_DSN"),