Leverage the email service function to send registration emails

[Nishit-Gopani]

• Send email when user register for first time

• Send email when user is Approved/Rejected

[shah-tejas]

• Create a service method to send registration related email to user.
• The service method accepts the Email Template Code and User (or user's email address) and calls the email service method (created by #49)

Acceptance Criteria:

• User received email when new account is created
• User receives an email when their account is approved
• User receives an email when their account is rejects