65 feat/rate limiting and scheduling (#73)

* feat: add mail processor that gets triggered every 30 secs

* feat: create background process for sending queued mails

* fix: resolve the problem with the auto-refetching of the campaign after campaign creation with no campaigns prior

* feat: add enqueue for the emails sent with smtp server and minor UI fixes on sidebar

* feat: create migration file that adds rate_limit col

* feat: add rate-limiting for sending the mail from the queue using both smtp server and aws client

* feat:
update email delivery, bounce, open, and click rates tracking for the mails sent from the AWS server as use of rate-limiting
write test for the rate_limiting
refactor the mail_service.rs file

* fix: add the missing rate_limit field in server struct and its test files:

* fix: add the missing input field for the rate_limit on the server Form and fix the default values for the deafault_value and rate_limit input fields

* fix: refactor the rate limiting assertions

Author: Kanak1125

backend/Cargo.lock

@@ -45,7 +45,8 @@ axum-extra = { version = "0.10.0", features = ["multipart"] }
 csv = "1.3.1"
 
 lettre = "0.11.14"
-
+tokenbucket = "0.1.6"
+governor = "0.10.0"
 
 
 [dev-dependencies]

backend/Cargo.toml

@@ -0,0 +1,6 @@
+-- Rollback: Remove queuing and rate-limiting fields from mails table
+
+ALTER TABLE mails
+DROP COLUMN scheduled_at,
+DROP COLUMN attempts,
+DROP COLUMN last_error;

backend/migrations/2025-04-22-082248_add_additional_fields_to_mail_for_queueing/down.sql

@@ -0,0 +1,6 @@
+-- Migration: Add queuing and rate-limiting fields to mails table
+
+ALTER TABLE mails
+ADD COLUMN "scheduled_at" TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP NOT NULL,
+ADD COLUMN "attempts" INTEGER DEFAULT 0 NOT NULL,
+ADD COLUMN "last_error" TEXT;

backend/migrations/2025-04-22-082248_add_additional_fields_to_mail_for_queueing/up.sql

@@ -0,0 +1,3 @@
+-- Down Migration: remove the rate_limit column
+ALTER TABLE "servers"
+DROP COLUMN IF EXISTS "rate_limit";

backend/migrations/2025-04-24-050126_add__rate_limit__column/down.sql

@@ -0,0 +1,3 @@
+-- Up Migration: add the rate_limit column with a default value
+ALTER TABLE "servers"
+ADD COLUMN "rate_limit" INTEGER NOT NULL DEFAULT 60;