New HTMLRenderer service and documentation for all services

[Prakhar896]

Overview of changes:

• Added documentation for all services. To see it, hover over a service's initialisation to read some usage/description information.
• Commented out model auto-detection and importing due to arbitrary issue pertaining the disappearance of some foreign keys
• New HTMLRenderer service that helps you render HTML templates. Useful for emailing purposes. Usage information below.

Using HTMLRenderer

1. Create HTML templates in the ./views directory. Recommended to create email templates in the ./views/emails folder.
2. Where you want to insert values, write {{ <KEY_NAME_HERE> }}. For example, to insert the value for key username, you would write {{ username }}.
3. Import HTMLRenderer from ./services/HTMLRenderer
4. Call HTMLRenderer.render and pass in the location of the template relative to the ./views directory as value as a key-value dictionary object with the values you want to fill in. Example call below.

const path = require('path')
const HTMLRenderer = require('./services/HTMLRenderer')
const htmlString = HTMLRenderer.render(path.join("emails", "ReservationConfirmation.html"), {
    username: "John Doe",
    email: "email@example.com",
    reservationReference: "ABC123"
})