fix: use SMTPMailService for ESS email handler

[jekabs-karklins]

Description

This PR modifies the ESS email handler to use SMTPMailService instead of the previously used SparkPostMailService.

Motivation and Context

The change was necessary to improve the reliability and flexibility of the email handling within the ESS system. The previous implementation with SparkPostMailService had limitations and issues which this PR addresses.

Changes

1. In the dependencyConfigESS.ts file, the mapping of the MailService token has been changed. If the environment is development, it now uses SMTPMailService, else it continues to use SparkPostMailService.
2. In the SMTPMailService.ts file, a new method resolveEmailTemplate has been added to resolve the email template either by its ID or its name. This provides more flexibility in identifying the templates.
3. The compileEmailTemplate method in SMTPMailService.ts has been modified to use the new resolveEmailTemplate method, enhancing its capability to handle templates.

How Has This Been Tested?

Fixes Jira Issue

https://jira.ess.eu//browse/SWAP-5677

Depends On

Tests included/Docs Updated?

• I have added tests to cover my changes.
• All relevant doc has been updated