chore: Upgrade to Ruby 3.2.1 & Rails 6.0

* chore: upgrade to rails 6.0

* chore: upgrade ruby to 3.2.1

* chore: upgrade bundler

* chore: upgrade execjs

* chore: upgrade to rails 6.1

* chore: switch to sentry-ruby from raven

* chore: add extra platforms to gemfile

lib/postal/smtp_server/server.rb

@@ -113,8 +113,8 @@ module Postal
                 monitor.value = client
               rescue StandardError => e
                 # If something goes wrong, log as appropriate and disconnect the client
-                if defined?(Raven)
-                  Raven.capture_exception(e, extra: { log_id: begin
+                if defined?(Sentry)
+                  Sentry.capture_exception(e, extra: { log_id: begin
                     client.id
                   rescue StandardError
                     nil
@@ -227,8 +227,8 @@ module Postal
               rescue StandardError => e
                 # Something went wrong, log as appropriate
                 client_id = client ? client.id : "------"
-                if defined?(Raven)
-                  Raven.capture_exception(e, extra: { log_id: begin
+                if defined?(Sentry)
+                  Sentry.capture_exception(e, extra: { log_id: begin
                     client.id
                   rescue StandardError
                     nil