chore: Set statement timeout for Postgres (#6641)

By default, Rails does not set a timeout on database statements. For example, this will run for a full day, even if your ruby process goes away. But it's configurable in the database.yml with the statement_timeout variable.

Hence we are enforcing a 14s timeout by default. Migration commands inside chatwoot will run with a 10 minutes timeout. For specific cases like migrations, we can override this timeout using the environment variable POSTGRES_STATEMENT_TIMEOUT while starting a new rails console.

Test the timeouts from the rails console using.

```
ActiveRecord::Base.connection.execute("SELECT pg_sleep(15);")
```

ref: https://github.com/ankane/the-ultimate-guide-to-ruby-timeouts#postgresql
ref: https://til.hashrocket.com/posts/b44baf657d-railspg-statement-timeout-

deployment/setup_20.04.sh

@@ -362,7 +362,7 @@ EOF
 function run_db_migrations(){
   sudo -i -u chatwoot << EOF
   cd chatwoot
-  RAILS_ENV=production bundle exec rails db:chatwoot_prepare
+  RAILS_ENV=production POSTGRES_STATEMENT_TIMEOUT=600s bundle exec rails db:chatwoot_prepare
 EOF
 }
 
@@ -574,7 +574,7 @@ The database migrations had not run as Postgres and Redis were not installed
 as part of the installation process. After modifying the environment
 variables (in the .env file) with your external database credentials, run
 the database migrations using the below command.
-'RAILS_ENV=production bundle exec rails db:chatwoot_prepare'.
+'RAILS_ENV=production POSTGRES_STATEMENT_TIMEOUT=600s bundle exec rails db:chatwoot_prepare'.
 ***************************************************************************
 
 EOF
@@ -744,7 +744,7 @@ function upgrade() {
   rake assets:precompile RAILS_ENV=production
 
   # Migrate the database schema
-  RAILS_ENV=production bundle exec rake db:migrate
+  RAILS_ENV=production POSTGRES_STATEMENT_TIMEOUT=600s bundle exec rake db:migrate
 
 EOF